Publication List of Boris Motik
In Journals
Bernardo Cuenca Grau, Boris Motik, Giorgos Stoilos, and Ian Horrocks. Completeness Guarantees for Incomplete Ontology Reasoners: Theory and Practice. Journal of Artificial Intelligence Research, 43:419–476, 2012.
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journal = "Journal of Artificial Intelligence Research",
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To achieve scalability of query answering, the developers of Semantic Web
applications are often forced to use incomplete OWL 2 reasoners, which
fail to derive all answers for at least one query, ontology, and data set. The
lack of completeness guarantees, however, may be unacceptable for applications
in areas such as health care and defence, where missing answers can adversely
affect the application's functionality. Furthermore, even if an application
can tolerate some level of incompleteness, it is often advantageous to
estimate how many and what kind of answers are being lost.
In this paper, we present a novel logic-based framework that allows one to
check whether a reasoner is complete for a given query $\Q$ and ontology
$\T$—that is, whether the reasoner is guaranteed to compute all answers to
$\Q$ w.r.t. $\T$ and an arbitrary data set $\A$. Since ontologies and typical
queries are often fixed at application design time, our approach allows
application developers to check whether a reasoner known to be incomplete in
general is actually complete for the kinds of input relevant for the
application.
We also present a technique that, given a query $\Q$, an ontology $\T$, and
reasoners $R_1$ and $R_2$ that satisfy certain assumptions, can be used to
determine whether, for each data set $\A$, reasoner $R_1$ computes more
answers to $\Q$ w.r.t. $\T$ and $\A$ than reasoner $R_2$. This allows
application developers to select the reasoner that provides the highest degree
of completeness for $\Q$ and $\T$ that is compatible with the application's
scalability requirements.
Our results thus provide a theoretical and practical foundation for the design
of future ontology-based information systems that maximise scalability while
minimising or even eliminating incompleteness of query answers.
Birte Glimm, Ian Horrocks, Boris Motik, and Giorgos Stoilos. A Novel Approach to Ontology Classification. Journal of Web Semantics: Science, Services and Agents on the World Wide Web, 2012. Accepted for publication.
@Article{ghmg12ontology-classification,
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Ontology classification—the computation of the subsumption hierarchies for
classes and properties—is a core reasoning service provided by all OWL
reasoners known to us. A popular algorithm for computing the class hierarchy
is the so-called Enhanced Traversal (ET) algorithm. In this paper we present a
new classification algorithm that attempts to address certain shortcomings of
ET and improve its performance. Apart from classification of classes, we also
consider object and data property classification. Using several simple
examples, we show that the algorithms commonly used to implement these tasks
are incomplete even for relatively weak ontology languages. Furthermore, we
show that property classification can be reduced to class classification,
which allows us to classify properties using our optimised algorithm. We
implemented all our algorithms in the OWL reasoner HermiT. The results of our
performance evaluation show significant performance improvements on several
well-known ontologies.
Boris Motik. Representing and Querying Validity Time in RDF and OWL: A Logic-Based Approach. Journal of Web Semantics: Science, Services and Agents on the World Wide Web, 12–13:3–21, 2012.
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RDF(S) and OWL 2 can currently represent only static information. In practice,
however, the truth of statements often changes with time. Semantic Web
applications often need to represent such changes and reason about them. In
this paper we present a logic-based approach for representing validity time in
RDF(S) and OWL 2. Unlike the existing proposals, our approach is applicable to
nondeterministic entailment relations and/or entailment relations that involve
existential quantification, such as the OWL 2 Direct Entailment and the OWL 2
RDF-Based Entailment. We also present an extension of SPARQL that can be used
to query temporal RDF(S) and OWL 2. Moreover, we present a general query
evaluation algorithm that can be used with all entailment relations used in
the Semantic Web. Finally, we present two optimizations of the algorithm that
are applicable to entailment relations characterized by a set of deterministic
rules, such RDF(S) and OWL 2 RL/RDF Entailment.
Boris Motik and Riccardo Rosati. Reconciling Description Logics and Rules. Journal of the ACM, 57(5):1–62, 2010.
@Article{mr10mknf-rules,
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Description logics (DLs) and rules are formalisms that emphasize
different aspects of knowledge representation: whereas DLs are
focused on specifying and reasoning about conceptual knowledge,
rules are focused on nonmonotonic inference. Many applications,
however, require features of both DLs and rules. Developing a
formalism that integrates DLs and rules would be a natural outcome
of a large body of research in knowledge representation and
reasoning of the last two decades; however, achieving this goal is
very challenging and the approaches proposed thus far have not fully
reached it. In this paper, we present a hybrid formalism of
\MKNFplus knowledge bases, which integrates DLs and rules in
a coherent semantic framework. Achieving seamless integration is
nontrivial, since DLs use an open-world assumption, while the rules
are based on a closed-world assumption. We overcome this discrepancy
by basing the semantics of our formalism on the logic of minimal
knowledge and negation as failure (MKNF) by Lifschitz. We present
several algorithms for reasoning with \MKNFplus knowledge bases,
each suitable to different kinds of rules, and establish tight
complexity bounds.
Boris Motik, Rob Shearer, and Ian Horrocks. Hypertableau Reasoning for Description Logics. Journal of Artificial Intelligence Research, 36:165–228, 2009.
@Article{msh09hypertableau,
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We present a novel reasoning calculus for the description logic
SHOIQplus—a knowledge representation formalism with applications
in areas such as the Semantic Web. Unnecessary nondeterminism and
the construction of large models are two primary sources of
inefficiency in the tableau-based reasoning calculi used in
state-of-the-art reasoners. In order to reduce nondeterminism, we
base our calculus on hypertableau and hyperresolution calculi, which
we extend with a blocking condition to ensure termination. In order
to reduce the size of the constructed models, we introduce
anywhere pairwise blocking. We also present an improved
nominal introduction rule that ensures termination in the presence
of nominals, inverse roles, and number restrictions—a combination
of DL constructs that has proven notoriously difficult to handle.
Our implementation shows significant performance improvements over
state-of-the-art reasoners on several well-known ontologies.
Héctor Pérez-Urbina, Boris Motik, and Ian Horrocks. Tractable Query Answering and Rewriting under Description Logic Constraints. Journal of Applied Logic, 8(2):151–232, 2009.
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Answering queries over an incomplete database w.r.t. a set of
constraints is an important computational task with applications in
fields as diverse as information integration and metadata management
in the semantic Web. Description Logics (DLs) are constraint
languages that have been extensively studied with the
goal of providing useful modeling constructs while keeping the query
answering problem decidable. For many DLs, query answering under
constraints can be solved via query rewriting: given a conjunctive
query $Q$ and a set of DL constraints $\tbox$, the query $Q$ can be
transformed into a datalog query $Q_\tbox$ that takes into account
the semantic consequences of $\tbox$; then, to obtain answers to $Q$
w.r.t. $\tbox$ and some (arbitrary) database instance $\abox$, one
can simply evaluate $Q_\tbox$ over $\abox$ using existing
(deductive) database technology, without taking $\tbox$ into
account. In this paper, we present a novel query rewriting algorithm
that handles constraints modeled in the DL \ELHIOneg and use it to
show that answering conjunctive queries in this setting is
PTime-complete w.r.t. data complexity. Our algorithm deals with
various description logics of the \EL and \DLlite families and is
worst-case optimal w.r.t. data complexity for all of them.
Boris Motik, Bernardo Cuenca Grau, Ian Horrocks, and Ulrike Sattler. Representing Ontologies Using Description Logics, Description Graphs, and Rules. Artificial Intelligence, 173(14):1275–1309, 2009.
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Description logics (DLs) are a family of state-of-the-art knowledge
representation languages, and their expressive power has been
carefully crafted to provide useful knowledge modeling primitives
while allowing for practically effective decision procedures for the
basic reasoning problems. Recent experience with DLs, however, has
shown that their expressivity is often insufficient to accurately
describe structured objects—objects whose parts are
interconnected in arbitrary, rather than tree-like ways. DL
knowledge bases describing structured objects are therefore usually
underconstrained, which precludes the entailment of certain
consequences and causes performance problems during reasoning.
To address this problem, we propose an extension of DL languages
with description graphs—a knowledge modeling construct that
can accurately describe objects with parts connected in arbitrary
ways. Furthermore, to enable modeling the conditional aspects of
structured objects, we also extend DLs with rules. We present an
in-depth study of the computational properties of such a formalism.
In particular, we first identify the sources of undecidability of
the general, unrestricted formalism. Based on that analysis, we then
investigate several restrictions of the general formalism that make
reasoning decidable. We present practical evidence that such a logic
can be used to model nontrivial structured objects. Finally, we
present a practical decision procedure for our formalism, as well as
tight complexity bounds.
Boris Motik, Ian Horrocks, and Ulrike Sattler. Bridging the Gap Between OWL and Relational Databases. Journal of Web Semantics: Science, Services and Agents on the World Wide Web, 7(2):74–89, 2009.
@Article{mhs09owl-dbs,
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Despite similarities between the Web Ontology Language (OWL) and
schema languages traditionally used in relational databases, systems
based on these languages exhibit quite different behavior in
practice. The schema statements in relational databases are usually
interpreted as integrity constraints and are used to check
whether the data is structured according to the schema. OWL allows
for axioms that resemble integrity constraints; however, these
axioms are interpreted under the standard first-order semantics and
not as checks. This often leads to confusion and is inappropriate in
certain data-centric applications. To explain the source of this
confusion, in this paper we compare OWL and relational databases
w.r.t. their schema languages and basic computational problems.
Based on this comparison, we extend OWL with integrity constraints
that capture the intuition behind similar statements in relational
databases. We show that, if the integrity constraints are satisfied,
they need not be considered while answering a broad range of
positive queries. Finally, we discuss several algorithms for
checking integrity constraint satisfaction, each of which is
suitable to different types of OWL knowledge bases.
Bernardo Cuenca Grau, Ian Horrocks, Boris Motik, Bijan Parsia, Peter Patel-Schneider, and Ulrike Sattler. OWL 2: The next step for OWL. Journal of Web Semantics: Science, Services and Agents on the World Wide Web, 6(4):309–322, 2008.
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Since achieving W3C recommendation status in 2004, the Web Ontology
Language (OWL) has been successfully applied to many problems in
computer science. Practical experience with OWL has been quite
positive in general; however, it has also revealed room for
improvement in several areas. We systematically analyze the
identified shortcomings of OWL, such as expressivity issues,
problems with its syntaxes, and deficiencies in the definition of
OWL species. Furthermore, we present an overview of OWL 2—an
extension to and revision of OWL that is currently being developed
within the W3C OWL Working Group. Many aspects of OWL have been
thoroughly reengineered in OWL 2, thus producing a robust platform
for future development of the language.
Ullrich Hustadt, Boris Motik, and Ulrike Sattler. Deciding Expressive Description Logics in the Framework of Resolution. Information & Computation, 206(5):579–601, 2008.
@Article{hms08deciding,
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We present a decision procedure for the description logic SHIQ
based on the basic superposition calculus, and show that it runs in
exponential time for unary coding of numbers. To derive our
algorithm, we extend basic superposition with a decomposition
inference rule, which transforms conclusions of certain inferences
into equivalent, but simpler clauses. This rule can be used for
general first-order theorem proving with any resolution-based
calculus compatible with the standard notion of redundancy.
Yevgeny Kazakov and Boris Motik. A Resolution-Based Decision Procedure for SHOIQ. Journal of Automated Reasoning, 40(2–3):89–116, 2008.
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We present a resolution-based decision procedure for the description
logic SHOIQ—the logic underlying the Semantic Web ontology
language OWL-DL. Our procedure is goal-oriented, and it naturally
extends a similar procedure for SHIQ, which has proven itself in
practice. Extending this procedure to SHOIQ using existing
techniques is not straightforward because of nominals, number
restrictions, and inverse roles—a combination known to cause
termination problems. We overcome this difficulty by using the basic
superposition calculus extended with custom simplification rules.
Boris Motik. On the Properties of Metamodeling in OWL. Journal of Logic and Computation, 17(4):617–637, 2007.
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A common practice in conceptual modeling is to separate the
conceptual from the data model. Although very intuitive, this
approach is inadequate for many complex domains, in which the
borderline between the two models is not clear-cut. Therefore,
OWL-Full, the most expressive of the Semantic Web ontology
languages, allows us to combine the conceptual and the data model by
a feature we refer to as metamodeling. In this paper, we show
that the semantics of metamodeling adopted in OWL-Full leads to the
undecidability of basic inference problems due to the free usage of
the built-in vocabulary. Based on this result, we propose two
alternative semantics for metamodeling: the contextual and
the HiLog semantics. We present several examples showing how
to use the latter semantics to axiomatize the interaction between
concepts and metaconcepts. Finally, we show that SHOIQD—the
description logic underlying OWL-DL—is still decidable when
extended with metamodeling under either semantics.
Ullrich Hustadt, Boris Motik, and Ulrike Sattler. Reasoning in Description Logics by a Reduction to Disjunctive Datalog. Journal of Automated Reasoning, 39(3):351–384, 2007.
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As applications of description logics proliferate, efficient
reasoning with knowledge bases containing many assertions becomes
ever more important. For such cases, we developed a novel reasoning
algorithm that reduces a SHIQ knowledge base to a disjunctive
datalog program while preserving the set of ground consequences.
Queries can then be answered in the resulting program while reusing
existing and practically proven optimization techniques of deductive
databases, such as join-order optimizations or magic sets. Moreover,
we use our algorithm to derive precise data complexity bounds: we
show that SHIQ is data complete for
NP, and we identify an
expressive fragment of SHIQ with polynomial data complexity.
Boris Motik, Ulrike Sattler, and Rudi Studer. Query Answering for OWL-DL with Rules. Journal of Web Semantics: Science, Services and Agents on the World Wide Web, 3(1):41–60, 2005.
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Both OWL-DL and function-free Horn rules are decidable fragments of
first-order logic with interesting, yet orthogonal expressive power.
A combination of OWL-DL and rules is desirable for the Semantic Web;
however, it might easily lead to the undecidability of interesting
reasoning problems. Here, we present a decidable such
combination where rules are required to be DL-safe: each
variable in the rule is required to occur in a non-DL-atom in the
rule body. We discuss the expressive power of such a combination and
present an algorithm for query answering in the related logic SHIQ
extended with DL-safe rules, based on a reduction to disjunctive
programs.
Raphael Volz, Steffen Staab, and Boris Motik. Incrementally Maintaining Materializations of Ontologies Stored in Logic Databases. Journal of Data Semantics II, 3360:1–34, 2005. LNCS, Springer.
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This article presents a technique to incrementally maintain materializations of ontological entailments. Materialization consists in precomputing and storing a set of implicit entailments, such that frequent and/or crucial queries to the ontology can be solved more efficiently. The central problem that arises with materialization is its maintenance when axioms change, viz. the process of propagating changes in explicit axioms to the stored implicit entailments. par When considering rule-enabled ontology languages that are operationalized in logic databases, we can distinguish two types of changes. Changes to the ontology will typically manifest themselves in changes to the rules of the logic program, whereas changes to facts will typically lead to changes in the extensions of logical predicates. The incremental maintenance of the latter type of changes has been studied extensively in the deductive database context and we apply the technique proposed in [30] for our purpose. The former type of changes has, however, not been tackled before. par In this article we elaborate on our previous papers [32, 33], which extend the approach of [30] to deal with changes in the logic program. Our approach is not limited to a particular ontology language but can be generally applied to arbitrary ontology languages that can be translated to Datalog programs, i.e. such as O-Telos, F-Logic [16] RDF(S), or Description Logic Programs [34].
Alexander Maedche, Boris Motik, and Ljiljana Stojanovic. Managing multiple and distributed ontologies on the Semantic Web. VLDB Journal, 12(4):286–302, 2003.
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In traditional software systems, significant attention is devoted to keeping modules well separated and coherent with respect to functionality, thus ensuring that changes in the system are localized to a handful of modules. Reuse is seen as the key method in reaching that goal. Ontology-based systems on the Semantic Web are just a special class of software systems, so the same principles apply. In this article, we present an integrated framework for managing multiple and distributed ontologies on the Semant ic Web. It is based on the representation model for ontologies, trading off between expressivity and tractability. In our framework, we provide features for reusing existing ontologies and for evolving them while retaining the consistency. The approach is implemented within KAON, the Karlsruhe Ontology and SemanticWeb tool suite.
Alexander Maedche, Boris Motik, Ljiljana Stojanovic, Rudi Studer, and Raphael Volz. Ontologies for Enterprise Knowledge Management. IEEE Intelligent Systems, 18(2):26–33, 2003.
@Article{mmssv03ontologies,
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Alexander Maedche and Boris Motik. Repräsentations- und Anfragesprachen für Ontologien—eine Übersicht. Datenbank-Spektrum, 6:43–53, 2003. In German.
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Semantik spielt in vielen Anwendungsgebieten eine wichtige Rolle. Eines der Anwendungsgebiete von semantischen Modellen ist die Informationsintegration, in welcher heterogene Informationsquellen zusammengef¸hrt werden. Dieser Beitrag gibt eine Einf¸hrung und ‹bersicht ¸ber den aktuellen Stand im Bereich der Repr‰sentations- und Anfragesprachen f¸r semantische Modelle und stellt den Karlsruher Ansatz KAON zur Ontologierepr‰sentation und -anfrage vor.
In Conferences
Despoina Magka, Boris Motik, and Ian Horrocks. Modelling Structured Domains Using Description Graphs and Logic Programming. In Proc. of the 9th Extended Semantic Web Conference (ESWC 2012), Heraklion, Greece, May 27–31 2012. To appear.
@InProceedings{mmh12dgs-and-lp,
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Although OWL 2 is widely used to describe complex objects such as chemical
molecules, it cannot represent `structural' features of chemical entities
(e.g., having a ring). A combination of rules and description graphs
(DGs) has been proposed as a possible solution, but it still exhibits several
drawbacks. In this paper we present a radically different approach that we
call Description Graph Logic Programs. Syntactically, our approach combines
DGs, rules, and OWL 2 RL axioms, but its semantics is defined via a
translation into logic programs under stable model semantics. The result is an
expressive OWL 2 RL-compatible formalism that is well suited for modelling
objects with complex structure.
Bernardo {Cuenca Grau}, Ian Horrocks, Markus Krötzsch, Clemens Kupke, Despoina Magka, Boris Motik, and Zhe Wang. Acyclicity Conditions and their Application to Query Answering in Description Logics. In Proc. of the 13th Int. Conf. on the Principles of Knowledge Representation and Reasoning (KR 2012), Rome, Italy, June 10–14 2012. To appear.
@InProceedings{ghkkmmw12acyclicity,
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Answering conjunctive queries (CQs) over a set of facts extended with
existential rules is a key problem in knowledge representation and databases.
This problem can be solved using the chase (aka materialisation)
algorithm; however, CQ answering is undecidable for general existential rules,
so the chase is not guaranteed to terminate. Several acyclicity
conditions provide sufficient conditions for chase termination. In this
paper, we present two novel such conditions—model-faithful acyclicity
(MFA) and model-summarising acyclicity (MSA)—that generalise many of
the acyclicity conditions known so far in the literature.
Materialisation provides the basis for several widely-used OWL 2 DL reasoners.
In order to avoid termination problems, many of these systems handle only the
OWL 2 RL profile of OWL 2 DL; furthermore, some systems go beyond OWL 2 RL,
but they provide no termination guarantees. In this paper we investigate
whether various acyclicity conditions can provide a principled and practical
solution to these problems. On the theoretical side, we show that query
answering for acyclic ontologies is of lower complexity than for general
ontologies. On the practical side, we show that many of the commonly used OWL
2 DL ontologies are MSA, and that the facts obtained via materialisation are
not too large. Thus, our results suggest that principled extensions to
materialisation-based OWL 2 DL reasoners may be practically feasible.
Boris Motik, Ian Horrocks, and Su Myeon Kim. Delta-Reasoner: A Semantic Web Reasoner for an Intelligent Mobile Platform. In Proc. of the 21st Int. World Wide Web Conference (WWW 2012), Industry Track, Lyon, France, April 16–20 2012. To appear.
@InProceedings{mhk12delta-reasoner,
author = "Boris Motik and Ian Horrocks and Su Myeon Kim",
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To make mobile device applications more intelligent, one can combine the
information obtained via device sensors with background knowledge in order to
deduce the user's current context, and then use this context to adapt the
application's behaviour to the user's needs. In this paper we describe
\Dreasoner, a key component of the Intelligent Mobile Platform (IMP), which
was designed to support context-aware applications running on mobile devices.
Context-aware applications and the mobile platform impose unusual requirements
on the reasoner, which we have met by incorporating advanced features such as
incremental reasoning and continuous query evaluation into our reasoner.
Although we have so far been able to conduct only a very preliminary
performance evaluation, our results are very encouraging: our reasoner
exhibits sub-second response time on ontologies whose size significantly
exceeds the size of the ontologies used in the IMP.
Giorgos Stoilos, Bernardo Cuenca Grau, Boris Motik, and Ian Horrocks. Repairing Ontologies for Incomplete Reasoners. In Lora Aroyo, Chris Welty, Harith Alani, Jamie Taylor, Abraham Bernstein, Lalana Kagal, Natasha Fridman Noy, and Eva Blomqvist, editors, Proc. of the 10th Int. Semantic Web Conf. (ISWC 2011), volume 7031 of LNCS, pages 681–696, Bonn, Germany, October 23–27 2011. Springer.
@InProceedings{sgmh11repairing,
author = "Giorgos Stoilos and Bernardo Cuenca Grau and Boris Motik and Ian Horrocks",
title = "{Repairing Ontologies for Incomplete Reasoners}",
booktitle = "Proc. of the 10th Int. Semantic Web Conf. (ISWC 2011)",
editor = "Lora Aroyo and Chris Welty and Harith Alani and Jamie Taylor and Abraham Bernstein and Lalana Kagal and Natasha Fridman Noy and Eva Blomqvist",
address = "Bonn, Germany",
month = "October 23--27",
year = "2011",
publisher = "Springer",
series = "LNCS",
volume = "7031",
pages = "681--696",
}
The need for scalable query answering often forces Semantic Web applications
to use incomplete OWL 2 reasoners, which in some cases fail to derive
all answers to a query. This is clearly undesirable, and in some applications
may even be unacceptable. To address this problem, we investigate the problem
of `repairing' an ontology $\T$—that is, computing an ontology $\R$ such
that a reasoner that is incomplete for $\T$ becomes complete when used with
$\T \cup \R$. We identify conditions on $\T$ and the reasoner that make this
possible, present a practical algorithm for computing $\R$, and present a
preliminary evaluation which shows that, in some realistic cases, repairs are
feasible to compute, reasonable in size, and do not significantly affect
reasoner performance.
Boris Motik. Representing and Querying Validity Time in RDF and OWL: A Logic-Based Approach. In Peter F. Patel-Schneider, Yue Pan, Pascal Hitzler, Peter Mika, Lei Zhang, Jeff Z. Pan, Ian Horrocks, and Birte Glimm, editors, Proc. of the 9th Int. Semantic Web Conf. (ISWC 2010), volume 6496 of LNCS, pages 550–565, Shanghai, China, November 7–11 2010. Springer.
@InProceedings{m10validity-time,
author = "Boris Motik",
title = "{Representing and Querying Validity Time in RDF and OWL: A Logic-Based Approach}",
booktitle = "Proc. of the 9th Int. Semantic Web Conf. (ISWC 2010)",
editor = "Peter F. Patel-Schneider and Yue Pan and Pascal Hitzler and Peter Mika and Lei Zhang and Jeff Z. Pan and Ian Horrocks and Birte Glimm",
address = "Shanghai, China",
month = "November 7--11",
year = "2010",
publisher = "Springer",
series = "LNCS",
volume = "6496",
pages = "550--565",
}
RDF(S) and OWL 2 currently support only static ontologies. In practice,
however, the truth of statements often changes with time, and Semantic Web
applications often need to represent such changes and reason about them. In
this paper we present a logic-based approach for representing validity time in
RDF and OWL. Unlike the existing proposals, our approach is applicable to
entailment relations that are not deterministic, such as the Direct Semantics
or the RDF-Based Semantics of OWL 2. We also extend SPARQL to temporal RDF
graphs and present a query evaluation algorithm. Finally, we present an
optimization of our algorithm that is applicable to entailment relations
characterized by a set of deterministic rules, such RDF(S) and OWL 2 RL/RDF
entailment.
Optimising Ontology Classification. Birte Glimm and Ian Horrocks and Boris Motik and Giorgos Stoilos. In Peter F. Patel-Schneider, Yue Pan, Pascal Hitzler, Peter Mika, Lei Zhang, Jeff Z. Pan, Ian Horrocks, and Birte Glimm, editors, Proc. of the 9th Int. Semantic Web Conf. (ISWC 2010), volume 6496 of LNCS, pages 225–240, Shanghai, China, November 7–11 2010. Springer.
@InProceedings{ghms10classification,
author = "Optimising Ontology Classification",
title = "{Birte Glimm and Ian Horrocks and Boris Motik and Giorgos Stoilos}",
booktitle = "Proc. of the 9th Int. Semantic Web Conf. (ISWC 2010)",
editor = "Peter F. Patel-Schneider and Yue Pan and Pascal Hitzler and Peter Mika and Lei Zhang and Jeff Z. Pan and Ian Horrocks and Birte Glimm",
address = "Shanghai, China",
month = "November 7--11",
year = "2010",
publisher = "Springer",
series = "LNCS",
volume = "6496",
pages = "225--240",
}
Ontology classification—the computation of subsumption hierarchies for
classes and properties—is one of the most important tasks for OWL reasoners.
Based on the algorithm by Shearer and Horrocks \cite{Rob09a}, we present a new
classification procedure that addresses several open issues of the original
algorithm, and that uses several novel optimisations in order to achieve
superior performance. We also consider the classification of (object and data)
properties. We show that algorithms commonly used to implement that task are
incomplete even for relatively weak ontology languages. Furthermore, we show
how to reduce the property classification problem into a standard (class)
classification problem, which allows reasoners to classify properties using
our optimised procedure. We have implemented our algorithms in the OWL HermiT
reasoner, and we present the results of a performance evaluation.
Birte Glimm, Ian Horrocks, and Boris Motik. Optimized Description Logic Reasoning via Core Blocking. In Jürgen Giesl and Reiner Hähnle, editors, Proc. of the 5th Int. Joint Conf. on Automated Reasoning (IJCAR 2010), volume 6173 of LNCS, pages 457–471, Edinburgh, UK, July 16–19 2010. Springer.
@InProceedings{ghm10core-blocking,
author = "Birte Glimm and Ian Horrocks and Boris Motik",
title = "{Optimized Description Logic Reasoning via Core Blocking}",
booktitle = "Proc. of the 5th Int. Joint Conf. on Automated Reasoning (IJCAR 2010)",
editor = "J{\"u}rgen Giesl and Reiner H{\"a}hnle",
address = "Edinburgh, UK",
month = "July 16--19",
year = "2010",
publisher = "Springer",
series = "LNCS",
volume = "6173",
pages = "457--471",
}
State of the art reasoners for expressive description logics, such as those
that underpin the OWL ontology language, are typically based on highly
optimized implementations of (hyper)tableau algorithms. Despite numerous
optimizations, certain ontologies encountered in practice still pose
significant challenges to such reasoners, mainly because of the size of the
model abstractions that they construct. To address this problem, we propose a
new blocking technique that tries to identify and halt redundant construction
at a much earlier stage than standard blocking techniques. An evaluation of a
prototypical implementation in the HermiT reasoner shows that our technique
can dramatically reduce the size of constructed model abstractions and reduce
reasoning time.
Bernardo Cuenca Grau and Boris Motik. Pushing the Limits of Reasoning over Ontologies with Hidden Content. In Fangzhen Lin, Ulrike Sattler, and Miroslaw Truszczynski, editors, Proc. of the 12th Int. Conference on Principles of Knowledge Representation and Reasoning (KR 2010), pages 200–210, Toronto, ON, Canada, May 9–13 2010. AAAI Press.
@InProceedings{gm10pushing-ibq,
author = "Bernardo Cuenca Grau and Boris Motik",
title = "{Pushing the Limits of Reasoning over Ontologies with Hidden Content}",
booktitle = "Proc. of the 12th Int. Conference on Principles of Knowledge Representation and Reasoning (KR 2010)",
editor = "Fangzhen Lin and Ulrike Sattler and Miroslaw Truszczynski",
address = "Toronto, ON, Canada",
month = "May 9--13",
year = "2010",
publisher = "AAAI Press",
pages = "200--210",
}
There is currently a growing interest in techniques for hiding parts of the
signature of an ontology $\hid{\KB}$ that is being reused by another ontology
$\vis{\KB}$. Towards this goal, \citeA{ijcai09-paper} recently proposed the
import-by-query framework, which makes the content of $\hid{\KB}$
accessible through a limited query interface. If $\vis{\KB}$ reuses the
symbols from $\hid{\KB}$ in a certain restricted way, one can reason over
${\vis{\KB} \cup \hid{\KB}}$ by accessing only $\vis{\KB}$ and the query
interface. In this paper, we map out the landscape of the import-by-query
problem. We show that certain restrictions of our original framework are
strictly necessary to make reasoning possible, we propose extensions that
overcome some of the expressivity limitations, we present several novel
reasoning algorithms, and we outline the limitations of the new framework.
Héctor Pérez-Urbina, Ian Horrocks, and Boris Motik. Efficient Query Answering for OWL 2. In Abraham Bernstein, David R. Karger, Tom Heath, Lee Feigenbaum, Diana Maynard, Enrico Motta, and Krishnaprasad Thirunarayan, editors, Proc. of the 8th Int. Semantic Web Conference (ISWC 2009), volume 5823 of LNCS, pages 489–504, Chantilly, VA, USA, October 25–29 2009. Springer.
@InProceedings{puhm09query-OWL2,
author = "H{\'e}ctor P{\'e}rez-Urbina and Ian Horrocks and Boris Motik",
title = "{Efficient Query Answering for OWL 2}",
booktitle = "Proc. of the 8th Int. Semantic Web Conference (ISWC 2009)",
editor = "Abraham Bernstein and David R. Karger and Tom Heath and Lee Feigenbaum and Diana Maynard and Enrico Motta and Krishnaprasad Thirunarayan",
address = "Chantilly, VA, USA",
month = "October 25--29",
year = "2009",
publisher = "Springer",
series = "LNCS",
volume = "5823",
pages = "489--504",
}
The QL profile of OWL 2 has been designed so that it is possible to
use database technology for query answering via query rewriting.
% : a
% query is first transformed into a union of conjunctive queries
% (i.e., an SQL query) using the conceptual part of the ontology and
% then the evaluation of the rewritten query is delegated to the
% database where the instance data resides.
% In our previous work we
% presented a rewriting algorithm that can deal with various
% description logics of the \DLlite and \EL families—the bases for
% the QL and EL profiles of OWL 2. Our algorithm exhibits
% "pay-as-you-go'' behavior: in the case of \DLliteR, it produces a
% union of conjunctive queries.
We present a comparison of our resolution based rewriting algorithm
% algorithm scaled down to \DLliteR
with the standard %rewriting
algorithm proposed by Calvanese et al., implementing both and conducting
% We implemented both algorithms and conducted
an empirical evaluation using ontologies
and queries derived from realistic applications. The results
indicate that our algorithm produces significantly smaller
rewritings in most cases, which could be important for practicality
in realistic applications.
Bernardo Cuenca Grau, Boris Motik, and Yevgeny Kazakov. Import-by-Query: Ontology Reasoning under Access Limitations. In Craig Boutilier, editor, Proc. of the 21st Int. Joint Conf. on Artificial Intelligence (IJCAI 2009), pages 727–733, Pasadena, CA, USA, July 11–17 2009.
@InProceedings{cgmk09ibq,
author = "Bernardo Cuenca Grau and Boris Motik and Yevgeny Kazakov",
title = "{Import-by-Query: Ontology Reasoning under Access Limitations}",
booktitle = "Proc. of the 21st Int. Joint Conf. on Artificial Intelligence (IJCAI 2009)",
editor = "Craig Boutilier",
address = "Pasadena, CA, USA",
month = "July 11--17",
year = "2009",
pages = "727--733",
}
To enable ontology reuse, the Web Ontology Language (OWL) allows an
ontology $\vis{\KB}$ to import an ontology $\hid{\KB}$. To
reason with such a $\vis{\KB}$, a reasoner needs physical access to
the axioms of $\hid{\KB}$. For copyright and/or privacy reasons,
however, the authors of $\hid{\KB}$ might not want to publish the
axioms of $\hid{\KB}$; instead, they might prefer to provide an
oracle that can answer a (limited) set of queries over
$\hid{\KB}$, thus allowing $\vis{\KB}$ to import $\hid{\KB}$ "by
query.'' In this paper, we study import-by-query algorithms,
which can answer questions about ${\vis{\KB} \cup \hid{\KB}}$ by
accessing only $\vis{\KB}$ and the oracle. We show that no such
algorithm exists in general, and present restrictions under which
importing by query becomes feasible.
Boris Motik and Ian Horrocks. OWL Datatypes: Design and Implementation. In Amit P. Sheth, Steffen Staab, Mike Dean, Massimo Paolucci, Diana Maynard, Timothy Finin, and Krishnaprasad Thirunarayan, editors, Proc. of the 7th Int. Semantic Web Conference (ISWC 2008), volume 5318 of LNCS, pages 307–322, Karlsruhe, Germany, October 26–30 2008. Springer.
@InProceedings{mh08datatypes,
author = "Boris Motik and Ian Horrocks",
title = "{OWL Datatypes: Design and Implementation}",
booktitle = "Proc. of the 7th Int. Semantic Web Conference (ISWC 2008)",
editor = "Amit P. Sheth and Steffen Staab and Mike Dean and Massimo Paolucci and Diana Maynard and Timothy Finin and Krishnaprasad Thirunarayan",
address = "Karlsruhe, Germany",
month = "October 26--30",
year = "2008",
publisher = "Springer",
series = "LNCS",
volume = "5318",
pages = "307--322",
}
We analyze the datatype system of OWL and OWL 2, and discuss certain
nontrivial consequences of its definition, such as the extensibility
of the set of supported datatypes and complexity of reasoning. We
also argue that certain datatypes from the list of normative
datatypes in the current OWL 2 Working Draft are inappropriate and
should be replaced with different ones. Finally, we present an
algorithm for datatype reasoning. Our algorithm is modular in the
sense that it can handle any datatype that supports certain basic
operations. We show how to implement these operations for number and
string datatypes.
Boris Motik, Bernardo Cuenca Grau, Ian Horrocks, and Ulirke Sattler. Representing Structured Objects using Description Graphs. In Gerhard Brewka and J'{e}r^{o}me Lang, editors, Proc. of the 11th Int. Joint Conf. on Principles of Knowledge Representation and Reasoning (KR 2008), pages 296–306, Sydney, NSW, Australia, August 16–19 2008. AAAI Press.
@InProceedings{mghs08description-graphs,
author = "Boris Motik and Bernardo Cuenca Grau and Ian Horrocks and Ulirke Sattler",
title = "{Representing Structured Objects using Description Graphs}",
booktitle = "Proc. of the 11th Int. Joint Conf. on Principles of Knowledge Representation and Reasoning (KR 2008)",
editor = "Gerhard Brewka and J'{e}r^{o}me Lang",
address = "Sydney, NSW, Australia",
month = "August 16--19",
year = "2008",
publisher = "AAAI Press",
pages = "296--306",
}
State-of-the-art ontology languages are often not sufficiently
expressive to accurately represent domains consisting of objects
connected in a complex way. As a possible remedy, in our previous
work we have proposed an extension of ontology languages with
description graphs. In this paper, we extend this formalism
by allowing for multiple graphs that can be combined in complex
ways, thus obtaining a powerful language for modeling structured
objects. By imposing a particular acyclicity restriction on
the relationships between the graphs, we ensure that checking
satisfiability of knowledge bases expressed in our language is
decidable. We also present a practical reasoning algorithm.
Boris Motik and Ian Horrocks. Individual Reuse in Description Logic Reasoning. In Alessandro Armando, Peter Baumgartner, and Gilles Dowek, editors, Proc. of the 4th Int. Joint Conf. on Automated Reasoning (IJCAR 2008), volume 5195 of LNAI, pages 242–258, Sydney, NSW, Australia, August 12–15 2008. Springer.
@InProceedings{mh08reuse,
author = "Boris Motik and Ian Horrocks",
title = "{Individual Reuse in Description Logic Reasoning}",
booktitle = "Proc. of the 4th Int. Joint Conf. on Automated Reasoning (IJCAR 2008)",
editor = "Alessandro Armando and Peter Baumgartner and Gilles Dowek",
address = "Sydney, NSW, Australia",
month = "August 12--15",
year = "2008",
publisher = "Springer",
series = "LNAI",
volume = "5195",
pages = "242--258",
}
Tableau calculi are the state-of-the-art for reasoning in
description logics (DL). Despite recent improvements, tableau-based
reasoners still cannot process certain knowledge bases (KBs), mainly
because they end up building very large models. To address this, we
propose a tableau calculus with individual reuse: to satisfy
an existential assertion, our calculus nondeterministically tries to
reuse individuals from the model generated thus far. We present two
expansion strategies: one is applicable to the DL \ELOH and
gives us a worst-case optimal algorithm, and the other is applicable
to the DL SHOIQ. Using this technique, our reasoner can process
several KBs that no other reasoner can.
Thanh Tran Duc, Peter Haase, Boris Motik, Bernardo Cuenca Grau, and Ian Horrocks. Metalevel Information in Ontology-Based Applications. In Dieter Fox and Carla P. Gomes, editors, Proc. of the 23rd AAAI Conf. on Artificial Intelligence (AAAI 2008), pages 1237–1242, Chicago, IL, USA, July 13–17 2008. AAAI Press.
@InProceedings{dhmgh08-metalevel-information,
author = "Thanh Tran Duc and Peter Haase and Boris Motik and Bernardo Cuenca Grau and Ian Horrocks",
title = "{Metalevel Information in Ontology-Based Applications}",
booktitle = "Proc. of the 23rd AAAI Conf. on Artificial Intelligence (AAAI 2008)",
editor = "Dieter Fox and Carla P. Gomes",
address = "Chicago, IL, USA",
month = "July 13--17",
year = "2008",
publisher = "AAAI Press",
pages = "1237--1242",
}
Applications of Semantic Web technologies often require the
management of metalevel information—that is, information
that provides additional detail about domain-level information, such
as provenance or access rights policies. Existing OWL-based tools
provide little or no support for the representation and management
of metalevel information. To fill this gap, we propose a framework
based on metaviews—ontologies that describe facts in the
application domain. We have implemented our framework in the KAON2
reasoner, and have successfully applied it in a nontrivial scenario.
Boris Motik, Bernardo Cuenca Grau, and Ulrike Sattler. Structured Objects in OWL: Representation and Reasoning. In Jinpeng Huai, Robin Chen, Hsiao-Wuen Hon, Yunhao Liu, Wei-Ying Ma, Andrew Tomkins, and Xiaodong Zhang, editors, Proc. of the 17th Int. World Wide Web Conference (WWW 2008), pages 555–564, Beijing, China, April 21–25 2008. ACM Press.
@InProceedings{mgs08structured-objects,
author = "Boris Motik and Bernardo Cuenca Grau and Ulrike Sattler",
title = "{Structured Objects in OWL: Representation and Reasoning}",
booktitle = "Proc. of the 17th Int. World Wide Web Conference (WWW 2008)",
editor = "Jinpeng Huai and Robin Chen and Hsiao-Wuen Hon and Yunhao Liu and Wei-Ying Ma and Andrew Tomkins and Xiaodong Zhang",
address = "Beijing, China",
month = "April 21--25",
year = "2008",
publisher = "ACM Press",
pages = "555--564",
}
Applications of semantic technologies often require the
representation of and reasoning with structured
objects—that is, objects composed of parts connected in complex
ways. Although OWL is a general and powerful language, its class
descriptions and axioms cannot be used to describe arbitrarily
connected structures. An OWL representation of structured objects
can thus be underconstrained, which reduces the inferences that can
be drawn and causes performance problems in reasoning. To address
these problems, we extend OWL with description graphs, which
allow for the description of structured objects in a simple and
precise way. To represent conditional aspects of the domain, we also
allow for SWRL-like rules over description graphs. Based on an
observation about the nature of structured objects, we ensure
decidability of our formalism. We also present a hypertableau-based
decision procedure, which we implemented in the HermiT reasoner. To
evaluate its performance, we have extracted description graphs from
the GALEN and FMA ontologies, classified them successfully, and even
detected a modeling error in GALEN.
Christine Golbreich, Matthew Horridge, Ian Horrocks, Boris Motik, and Rob Shearer. OBO and OWL: Leveraging Semantic Web Technologies for the Life Sciences. In Karl Aberer, Key-Sun Choi, Natasha Fridman Noy, Dean Allemang, Kyung-Il Lee, Lyndon J. B. Nixon, Jennifer Golbeck, Peter Mika, Diana Maynard, Riichiro Mizoguchi, Guus Schreiber, and Philippe Cudré-Mauroux, editors, Proc. of the 6th Int. Semantic Web Conference (ISWC 2007), volume 4825 of LNCS, pages 169–182, Busan, Korea, November 11-15 2007. Springer.
@InProceedings{ghhms07obo-and-owl,
author = "Christine Golbreich and Matthew Horridge and Ian Horrocks and Boris Motik and Rob Shearer",
title = "{OBO and OWL: Leveraging Semantic Web Technologies for the Life Sciences}",
booktitle = "Proc. of the 6th Int. Semantic Web Conference (ISWC 2007)",
editor = "Karl Aberer and Key-Sun Choi and Natasha Fridman Noy and Dean Allemang and Kyung-Il Lee and Lyndon J. B. Nixon and Jennifer Golbeck and Peter Mika and Diana Maynard and Riichiro Mizoguchi and Guus Schreiber and Philippe Cudr{\'e}-Mauroux",
address = "Busan, Korea",
month = "November 11-15",
year = "2007",
publisher = "Springer",
series = "LNCS",
volume = "4825",
pages = "169--182",
}
OBO is an ontology language that has often been used for modeling
ontologies in the life sciences. Its definition is relatively
informal, so, in this paper, we provide a clear specification for
OBO syntax and semantics via a mapping to OWL. This mapping also
allows us to apply existing Semantic Web tools and techniques to
OBO. We show that Semantic Web reasoners can be used to efficiently
reason with OBO ontologies. Furthermore, we show that grounding the
OBO language in formal semantics is useful for the ontology
development process: using an OWL reasoner, we detected a likely
modeling error in one OBO ontology.
Boris Motik, Rob Shearer, and Ian Horrocks. Optimized Reasoning in Description Logics using Hypertableaux. In Frank Pfenning, editor, Proc. of the 21st Conference on Automated Deduction (CADE-21), volume 4603 of LNAI, pages 67–83, Bremen, Germany, July 17–20 2007. Springer.
@InProceedings{msh07optimizing,
author = "Boris Motik and Rob Shearer and Ian Horrocks",
title = "{Optimized Reasoning in Description Logics using Hypertableaux}",
booktitle = "Proc. of the 21st Conference on Automated Deduction (CADE-21)",
editor = "Frank Pfenning",
address = "Bremen, Germany",
month = "July 17--20",
year = "2007",
publisher = "Springer",
series = "LNAI",
volume = "4603",
pages = "67--83",
}
We present a novel reasoning calculus for Description Logics
(DLs)—knowledge representation formalisms with applications in
areas such as the Semantic Web. In order to reduce the
nondeterminism due to general inclusion axioms, we base our calculus
on hypertableau and hyperresolution calculi, which we extend with a
blocking condition to ensure termination. To prevent the calculus
from generating large models, we introduce "anywhere"
pairwise blocking. Our preliminary implementation shows significant
performance improvements on several well-known ontologies. To the
best of our knowledge, our reasoner is currently the only one that
can classify the original version of the GALEN terminology.
Boris Motik, Ian Horrocks, and Ulrike Sattler. Bridging the Gap Between OWL and Relational Databases. In Carey L. Williamson, Mary Ellen Zurko, Peter F. Patel-Schneider, and Prashant J. Shenoy, editors, Proc. of the 16th International World Wide Web Conference (WWW 2007), pages 807–816, Banff, AB, Canada, May 8–12 2007. ACM Press.
@InProceedings{mhs07bridging,
author = "Boris Motik and Ian Horrocks and Ulrike Sattler",
title = "{Bridging the Gap Between OWL and Relational Databases}",
booktitle = "Proc. of the 16th International World Wide Web Conference (WWW 2007)",
editor = "Carey L. Williamson and Mary Ellen Zurko and Peter F. Patel-Schneider and Prashant J. Shenoy",
address = "Banff, AB, Canada",
month = "May 8--12",
year = "2007",
publisher = "ACM Press",
pages = "807--816",
}
Schema statements in OWL are interpreted quite differently from
analogous statements in relational databases. If these statements
are meant to be interpreted as integrity constraints (ICs), OWL's
interpretation may seem confusing and/or inappropriate. Therefore,
we propose an extension of OWL with ICs that captures the intuition
behind ICs in relational databases. We discuss the algorithms for
checking IC satisfaction for different types of knowledge bases, and
show that, if the constraints are satisfied, we can disregard them
while answering a broad range of positive queries.
Boris Motik and Riccardo Rosati. A Faithful Integration of Description Logics with Logic Programming. In Manuela M. Veloso, editor, Proc. of the 20th Int. Joint Conference on Artificial Intelligence (IJCAI 2007), pages 477–482, Hyderabad, India, January 6–12 2007. Morgan Kaufmann Publishers.
@InProceedings{mr07dl-and-lp,
author = "Boris Motik and Riccardo Rosati",
title = "{A Faithful Integration of Description Logics with Logic Programming}",
booktitle = "Proc. of the 20th Int. Joint Conference on Artificial Intelligence (IJCAI 2007)",
editor = "Manuela M. Veloso",
address = "Hyderabad, India",
month = "January 6--12",
year = "2007",
publisher = "Morgan Kaufmann Publishers",
pages = "477--482",
}
Integrating description logics (DL) and logic programming (LP) would
produce a very powerful and useful formalism. However, DLs and LP
are based on quite different principles, so achieving a seamless
integration is not trivial. In this paper, we introduce hybrid
MKNF knowledge bases that faithfully integrate DLs with LP using
the logic of Minimal Knowledge and Negation as Failure (MKNF)
\cite{DBLP:conf/ijcai/Lifschitz91}. We also give reasoning
algorithms and tight data complexity bounds for several interesting
fragments of our logic.
Boris Motik, Ian Horrocks, Riccardo Rosati, and Ulrike Sattler. Can OWL and Logic Programming Live Together Happily Ever After? In Isabel F. Cruz, Stefan Decker, Dean Allemang, Chris Preist, Daniel Schwabe, Peter Mika, Michael Uschold, and Lora Aroyo, editors, Proc. of the 5th Int. Semantic Web Conference (ISWC 2006), volume 4273 of LNCS, pages 501–514, Athens, GA, USA, November 5–9 2006. Springer.
@InProceedings{mhs06happily,
author = "Boris Motik and Ian Horrocks and Riccardo Rosati and Ulrike Sattler",
title = "{Can OWL and Logic Programming Live Together Happily Ever After?}",
booktitle = "Proc. of the 5th Int. Semantic Web Conference (ISWC 2006)",
editor = "Isabel F. Cruz and Stefan Decker and Dean Allemang and Chris Preist and Daniel Schwabe and Peter Mika and Michael Uschold and Lora Aroyo",
address = "Athens, GA, USA",
month = "November 5--9",
year = "2006",
publisher = "Springer",
series = "LNCS",
volume = "4273",
pages = "501--514",
}
Logic programming (LP) is often seen as a way to overcome several
shortcomings of the Web Ontology Language (OWL), such as the
inability to model integrity constraints or perform closed-world
querying. However, the open-world semantics of OWL seems to be
fundamentally incompatible with the closed-world semantics of LP.
This has sparked a heated debate in the Semantic Web community,
resulting in proposals for alternative ontology languages based
entirely on logic programming. To help resolving this debate, we
investigate the practical use cases which seem to be addressed by
logic programming. In fact, many of these requirements have already
been addressed outside the Semantic Web. By drawing inspiration from
these existing formalisms, we present a novel logic of hybrid
MKNF knowledge bases, which seamlessly integrates OWL with LP. We
are thus capable of addressing the identified use cases without a
radical change in the architecture of the Semantic Web.
Boris Motik and Ulrike Sattler. A Comparison of Reasoning Techniques for Querying Large Description Logic ABoxes. In Miki Hermann and Andrei Voronkov, editors, Proc. of the 13th Int. Conference on Logic for Programming Artificial Intelligence and Reasoning (LPAR 2006), volume 4246 of LNCS, pages 227–241, Phnom Penh, Cambodia, November 13–17 2006. Springer.
@InProceedings{ms06kaon2,
author = "Boris Motik and Ulrike Sattler",
title = "{A Comparison of Reasoning Techniques for Querying Large Description Logic ABoxes}",
booktitle = "Proc. of the 13th Int. Conference on Logic for Programming Artificial Intelligence and Reasoning (LPAR 2006)",
editor = "Miki Hermann and Andrei Voronkov",
address = "Phnom Penh, Cambodia",
month = "November 13--17",
year = "2006",
publisher = "Springer",
series = "LNCS",
volume = "4246",
pages = "227--241",
}
Many modern applications of description logics (DLs) require
answering queries over large data quantities, structured according
to relatively simple ontologies. For such applications, we
conjectured that reusing ideas of deductive databases might improve
scalability of DL systems. Hence, in our previous work, we developed
an algorithm for reducing a DL knowledge base to a disjunctive
datalog program. To test our conjecture, we implemented our
algorithm in a new DL reasoner KAON2, which we describe in this
paper. Furthermore, we created a comprehensive test suite and used
it to conduct a performance evaluation. Our results show that, on
knowledge bases with large ABoxes but with simple TBoxes, our
technique indeed shows good performance; in contrast, on knowledge
bases with large and complex TBoxes, existing techniques still
perform better. This allowed us to gain important insights into
strengths and weaknesses of both approaches.
Yevgeny Kazakov and Boris Motik. A Resolution-Based Decision Procedure for SHOIQ. In Ulrich Furbach, John Harrison, and Natarajan Shankar, editors, Proc. of the 3rd Int. Joint Conference on Automated Reasoning (IJCAR 2006), volume 4130 of LNAI, pages 662–667, Seattle, WA, USA, August 17–20 2006. Springer.
@InProceedings{km06shoiq,
author = "Yevgeny Kazakov and Boris Motik",
title = "{A Resolution-Based Decision Procedure for SHOIQ}",
booktitle = "Proc. of the 3rd Int. Joint Conference on Automated Reasoning (IJCAR 2006)",
editor = "Ulrich Furbach and John Harrison and Natarajan Shankar",
address = "Seattle, WA, USA",
month = "August 17--20",
year = "2006",
publisher = "Springer",
series = "LNAI",
volume = "4130",
pages = "662--667",
}
We present a resolution-based decision procedure for the description
logic SHOIQ—the logic underlying the Semantic Web ontology
language OWL-DL. Our procedure is goal-oriented, and it naturally
extends a similar procedure for SHIQ, which has proven itself in
practice. Applying existing techniques for deriving saturation-based
decision procedures to SHOIQ is not straightforward due to
nominals, number restrictions, and inverse roles—a combination
known to cause termination problems. We overcome this difficulty by
using the basic superposition calculus, extended with custom
simplification rules.
Stephan Grimm, Boris Motik, and Chris Preist. Matching Semantic Service Descriptions with Local Closed-World Reasoning. In York Sure and John Domingue, editors, Proc. of the 3rd European Semantic Web Conference (ESWC 2006), volume 4011 of LNCS, pages 575–589, Budva, Montenegro, June 11–14 2006. Springer.
@InProceedings{gmp06matching,
author = "Stephan Grimm and Boris Motik and Chris Preist",
title = "{Matching Semantic Service Descriptions with Local Closed-World Reasoning}",
booktitle = "Proc. of the 3rd European Semantic Web Conference (ESWC 2006)",
editor = "York Sure and John Domingue",
address = "Budva, Montenegro",
month = "June 11--14",
year = "2006",
publisher = "Springer",
series = "LNCS",
volume = "4011",
pages = "575--589",
}
Semantic Web Services were developed with the goal of automating
the integration of business processes on the Web. The main idea is
to express the functionality of the services explicitly, using
semantic annotations. Such annotations can, for example, be used
for service discovery—the task of locating a service capable of
fulfilling a business request. In this paper, we present a
framework for annotating Web Services using description logics
(DLs), a family of knowledge representation formalisms widely used
in the Semantic Web. We show how to realise service discovery by
matching semantic service descriptions, applying DL inferencing.
Building on our previous work, we identify problems that occur in
the matchmaking process due to the open-world assumption when
handling incomplete service descriptions. We propose to use
autoepistemic extensions to DLs (ADLs) to overcome these problems.
ADLs allow for non-monotonic reasoning and for querying DL
knowledge bases under local closed-world assumption. We
investigate the use of epistemic operators of ADLs in service
descriptions, and show how they affect DL inferences in the
context of semantic matchmaking.
Boris Motik. On the Properties of Metamodeling in OWL. In Yolanda Gil, Enrico Motta, Richard V. Benjamins, and Mark Musen, editors, Proc. of the 4th Int. Semantic Web Conference (ISWC 2005), volume 3729 of LNCS, pages 548–562, Galway, Ireland, November 6–10 2005. Springer.
@InProceedings{m05metamodeling,
author = "Boris Motik",
title = "{On the Properties of Metamodeling in OWL}",
booktitle = "Proc. of the 4th Int. Semantic Web Conference (ISWC 2005)",
editor = "Yolanda Gil and Enrico Motta and Richard V. Benjamins and Mark Musen",
address = "Galway, Ireland",
month = "November 6--10",
year = "2005",
publisher = "Springer",
series = "LNCS",
volume = "3729",
pages = "548--562",
}
A common practice in conceptual modeling is to separate the
intensional from the extensional model. Although very intuitive,
this approach is inadequate for many complex domains, where the
borderline between the two models is not clear-cut. Therefore,
OWL-Full, the most expressive of the Semantic Web ontology
languages, allows combining the intensional and the extensional
model by a feature we refer to as metamodeling. In this
paper, we show that the semantics of metamodeling adopted in
OWL-Full leads to undecidability of basic inference problems, due to
free mixing of logical and metalogical symbols. Based on this
result, we propose two alternative semantics for metamodeling: the
contextual and the HiLog semantics. We show that
SHOIQ — a description logic underlying OWL-DL — extended with
metamodeling under either semantics is decidable. Finally, we show
how the latter semantics can be used in practice to axiomatize the
logical interaction between concepts and metaconcepts.
Ullrich Hustadt, Boris Motik, and Ulrike Sattler. Data Complexity of Reasoning in Very Expressive Description Logics. In Leslie Pack Kaelbling and Alessandro Saffiotti, editors, Proc. of the 19th Int. Joint Conference on Artificial Intelligence (IJCAI 2005), pages 466–471, Edinburgh, UK, July 30–August 5 2005. Morgan Kaufmann Publishers.
@InProceedings{hms05data,
author = "Ullrich Hustadt and Boris Motik and Ulrike Sattler",
title = "{Data Complexity of Reasoning in Very Expressive Description Logics}",
booktitle = "Proc. of the 19th Int. Joint Conference on Artificial Intelligence (IJCAI 2005)",
editor = "Leslie Pack Kaelbling and Alessandro Saffiotti",
address = "Edinburgh, UK",
month = "July 30--August 5",
year = "2005",
publisher = "Morgan Kaufmann Publishers",
pages = "466--471",
}
Data complexity of reasoning in description logics (DLs)
estimates the performance of reasoning algorithms measured in the
size of the ABox only. We show that, even for the very expressive DL
SHIQ, satisfiability checking is data complete for
NP. For
applications with large ABoxes, this can be a more accurate estimate
than the usually considered combined complexity, which is
ExpTime-complete. Furthermore, we identify an expressive fragment,
Horn-SHIQ, which is data complete for P, thus being very appealing
for practical usage.
Ullrich Hustadt, Boris Motik, and Ulrike Sattler. A Decomposition Rule for Decision Procedures by Resolution-based Calculi. In Franz Baader and Andrei Voronkov, editors, Proc. of the 11th Int. Conference on Logic for Programming Artificial Intelligence and Reasoning (LPAR 2004), volume 3452 of LNAI, pages 21–35, Montevideo, Uruguay, March 14–18 2005. Springer.
@InProceedings{hms04decomposition,
author = "Ullrich Hustadt and Boris Motik and Ulrike Sattler",
title = "{A Decomposition Rule for Decision Procedures by Resolution-based Calculi}",
booktitle = "Proc. of the 11th Int. Conference on Logic for Programming Artificial Intelligence and Reasoning (LPAR 2004)",
editor = "Franz Baader and Andrei Voronkov",
address = "Montevideo, Uruguay",
month = "March 14--18",
year = "2005",
publisher = "Springer",
volume = "3452",
series = "LNAI",
pages = "21--35",
}
Resolution-based calculi are among the most widely used calculi for
theorem proving in first-order logic. Numerous refinements of
resolution are nowadays available, such as e.g. basic
superposition, a calculus highly optimized for theorem proving with
equality. However, even such an advanced calculus does not restrict
inferences enough to obtain decision procedures for complex logics,
such as SHIQ. In this paper, we present a new decomposition
inference rule, which can be combined with any resolution-based
calculus compatible with the standard notion of redundancy. We
combine decomposition with basic superposition to obtain three new
decision procedures: (i) for the description logic SHIQ,
(ii) for the description logic ALCHIQb, and (iii) for
answering conjunctive queries over SHIQ knowledge bases. The first
two procedures are worst-case optimal and, based on the vast
experience in building efficient theorem provers, we expect them to
be suitable for practical usage.
Ullrich Hustadt, Boris Motik, and Ulrike Sattler. Reducing SHIQ- Description Logic to Disjunctive Datalog Programs. In Didier Dubois, Christopher A. Welty, and Mary-Anne Williams, editors, Proc. of the 9th Int. Conference on Principles of Knowledge Representation and Reasoning (KR 2004), pages 152–162, Whistler, Canada, June 2–5 2004. AAAI Press.
@InProceedings{hms04reducing,
author = "Ullrich Hustadt and Boris Motik and Ulrike Sattler",
title = "{Reducing $\mathcal{SHIQ}^-$ Description Logic to Disjunctive Datalog Programs}",
booktitle = "Proc. of the 9th Int. Conference on Principles of Knowledge Representation and Reasoning (KR 2004)",
editor = "Didier Dubois and Christopher A. Welty and Mary-Anne Williams",
address = "Whistler, Canada",
month = "June 2--5",
year = "2004",
publisher = "AAAI Press",
pages = "152--162",
}
As applications of description logics proliferate, efficient
reasoning with large ABoxes (sets of individuals with
descriptions) becomes ever more important. Motivated by the
prospects of reusing optimization techniques from deductive
databases, in this paper, we present a novel approach to checking
consistency of ABoxes, instance checking and query answering,
w.r.t. ontologies formulated using a slight restriction of the
description logic SHIQ. Our approach proceeds in three steps: (i)
the ontology is translated into first-order clauses, (ii) TBox and
RBox clauses are saturated using a resolution-based decision
procedure, and (iii) the saturated set of clauses is translated
into a disjunctive datalog program. Thus, query answering can be
performed using the resulting program, while applying all existing
optimization techniques, such as join-order optimizations or magic
sets. Equally important, the resolution-based decision procedure
we present is for unary coding of numbers worst-case optimal, i.e.
it runs in
ExpTime.
Ullrich Hustadt, Boris Motik, and Ulrike Sattler. Reasoning in Description Logics with a Concrete Domain in the Framework of Resolution. In Ramon López de Mántaras and Lorenza Saitta, editors, Proc. of the 16th European Conference on Artificial Intelligence (ECAI 2004), pages 353–357, Valencia, Spain, August 22–27 2004. IOS Press.
@InProceedings{hms04concrete,
author = "Ullrich Hustadt and Boris Motik and Ulrike Sattler",
title = "{Reasoning in Description Logics with a Concrete Domain in the Framework of Resolution}",
booktitle = "Proc. of the 16th European Conference on Artificial Intelligence (ECAI 2004)",
editor = "Ramon L{\'o}pez de M{\'a}ntaras and Lorenza Saitta",
address = "Valencia, Spain",
month = "August 22--27",
year = "2004",
publisher = "IOS Press",
pages = "353--357",
}
In description logics, concrete domains are used to model concrete
properties such as weight, name, or age, having concrete values
such as integers or strings, with built-in predicates, such
as <= or =. Until now, reasoning with concrete domains has
been studied predominantly in the context of tableaux and automata
calculi. In this paper, we present a general approach for concrete
domain reasoning in the resolution framework. We apply this
approach to devise an optimal decision procedure for SHIQD, the
extension of SHIQ with a restricted form of concrete domains,
serving as the logical underpinning of the web ontology language
OWL-DL.
Boris Motik, Ulrike Sattler, and Rudi Studer. Query Answering for OWL-DL with Rules. In Sheila A. McIlraith, Dimitris Plexousakis, and Frank van Harmelen, editors, Proc. of the 3rd Int. Semantic Web Conference (ISWC 2004), volume 3298 of LNCS, pages 549–563, Hiroshima, Japan, November 7–11 2004. Springer.
@InProceedings{mss04dl-safe,
author = "Boris Motik and Ulrike Sattler and Rudi Studer",
title = "{Query Answering for OWL-DL with Rules}",
booktitle = "Proc. of the 3rd Int. Semantic Web Conference (ISWC 2004)",
editor = "Sheila A. McIlraith and Dimitris Plexousakis and Frank van Harmelen",
month = "November 7--11",
address = "Hiroshima, Japan",
year = "2004",
publisher = "Springer",
volume = "3298",
series = "LNCS",
pages = "549--563",
}
Both OWL-DL and function-free Horn rules\footnote{Throughout this
paper, we use "rules" and "clauses" synonymously, following
\cite{HoPa04a}.} are decidable logics with interesting, yet
orthogonal expressive power: from the rules perspective, OWL-DL is
restricted to tree-like rules, but provides both existentially and
universally quantified variables and full, monotonic negation. From
the description logic perspective, rules are restricted to universal
quantification, but allow for the interaction of variables in
arbitrary ways. Clearly, a combination of OWL-DL and rules is
desirable for building Semantic Web ontologies, and several such
combinations have already been discussed. However, such a
combination might easily lead to the undecidability of interesting
reasoning problems. Here, we present a decidable such
combination which is, to the best of our knowledge, more general
than similar decidable combinations proposed so far. Decidability is
obtained by restricting rules to so-called DL-safe ones,
requiring each variable in a rule to occur in a non-DL-atom in the
rule body. We show that query answering in such a combined logic is
decidable, and we discuss its expressive power by means of a
non-trivial example. Finally, we present an algorithm for query
answering in SHIQD extended with DL-safe rules based on the
reduction to disjunctive datalog.
Gábor Nagypál and Boris Motik. A Fuzzy Model for Representing Uncertain, Subjective, and Vague Temporal Knowledge in Ontologies. In Robert Meersman, Zahir Tari, and Douglas C. Schmidt, editors, Proc. of the 2003 Int. Conference on Ontologies, Databases and Applications of SEmantics (ODBASE 2003), volume 2888 of LNCS, pages 906–923, Catania, Italy, November 3–7 2003. Springer.
@InProceedings{nm03fuzzy,
author = "G{\'a}bor Nagyp{\'a}l and Boris Motik",
title = "{A Fuzzy Model for Representing Uncertain, Subjective, and Vague Temporal Knowledge in Ontologies}",
booktitle = "Proc. of the 2003 Int. Conference on Ontologies, Databases and Applications of SEmantics (ODBASE 2003)",
editor = "Robert Meersman and Zahir Tari and Douglas C. Schmidt",
address = "Catania, Italy",
month = "November 3--7",
year = "2003",
publisher = "Springer",
series = "LNCS",
volume = "2888",
pages = "906--923",
}
Time modeling is a crucial feature in many application domains. However, temporal information often is not crisp, but is uncertain, subjective and vague. This is particularly true when representing historical information, as historical accounts are inherently imprecise. Similarly, we conjecture that in the Semantic Web representing uncertain temporal information will be a common requirement. Hence, existing approaches for temporal modeling based on crisp representation of time cannot be applied to these advanced modeling tasks. To overcome these difficulties, in this paper we present fuzzy interval-based temporal model capable of representing imprecise temporal knowledge. Our approach naturally subsumes existing crisp temporal models, i.e. crisp temporal relationships are intuitively represented in our system. Apart from presenting the fuzzy temporal model, we discuss how this model is integrated with the ontology model to allow annotating ontology definitions with time specifications.
Raphael Volz, Steffen Staab, and Boris Motik. Incremental Maintenance of Materialized Ontologies. In Robert Meersman, Zahir Tari, and Douglas C. Schmidt, editors, Proc. of the 2003 Int. Conference on Ontologies, Databases and Applications of SEmantics (ODBASE 2003), volume 2888 of LNCS, pages 707–724, Catania, Italy, November 3–7 2003. Springer.
@InProceedings{vsm03incremental,
author = "Raphael Volz and Steffen Staab and Boris Motik",
title = "{Incremental Maintenance of Materialized Ontologies}",
booktitle = "Proc. of the 2003 Int. Conference on Ontologies, Databases and Applications of SEmantics (ODBASE 2003)",
editor = "Robert Meersman and Zahir Tari and Douglas C. Schmidt",
address = "Catania, Italy",
month = "November 3--7",
year = "2003",
publisher = "Springer",
series = "LNCS",
volume = "2888",
pages = "707--724",
}
This paper discusses the incremental maintenance of materialized ontologies in a rule-enabled Semantic Web. Materialization allows to speed up query processing by explicating the implicit entailments which are sanctioned by the semantics of an ontology. The complexity of reasoning with the ontology is thereby shifted from query time to update time. We assume that materialization techniques will frequently be important to achieve a scalable Semantic Web, since read access to ontologies is predominant. Central to materialization are maintenance techniques that allow to incrementally update a materialization when changes occur. par We present a novel solution that allows to cope with changes in rules and facts. To achieve this we extend a known approach for the incremental maintenance of views in deductive databases. We show how our technique can be employed for a broad range of existing Web ontology languages, such as RDF/S and subsets of OWL and present a first evaluation.
Alexander Maedche, Boris Motik, Ljiljana Stojanovic, Rudi Studer, and Raphael Volz. An infrastructure for searching, reusing and evolving distributed ontologies. In Proc. of the 12th International World Wide Web Conference (WWW 2003), pages 439–448, Budapest, Hungary, May 20–24 2003. ACM Press.
@InProceedings{mmssv03infrastructure,
author = "Alexander Maedche and Boris Motik and Ljiljana Stojanovic and Rudi Studer and Raphael Volz",
title = "{An infrastructure for searching, reusing and evolving distributed ontologies}",
booktitle = "Proc. of the 12th International World Wide Web Conference (WWW 2003)",
address = "Budapest, Hungary",
month = "May 20--24",
year = "2003",
publisher = "ACM Press",
pages = "439--448",
}
The vision of the Semantic Web can only be realized through
proliferation of well-known ontologies describing different
domains. To enable interoperability in the Semantic Web, it will
be necessary to break these ontologies down into smaller,
well-focused units that may be reused. Currently, three problems
arise in that scenario. Firstly, it is difficult to locate
ontologies to be reused, thus leading to many ontologies modeling
the same thing. Secondly, current tools do not provide means for
reusing existing ontologies while building new ontologies.
Finally, ontologies are rarely static, but are being adapted to
changing requirements. Hence, an infrastructure for management of
ontology changes, taking into account dependencies between
ontologies is needed. In this paper we present such an
infrastructure addressing the aforementioned problems.
Raphael Volz, Daniel Oberle, Steffen Staab, and Boris Motik. KAON SERVER — A Semantic Web Management System. In Alternate Track Proc. of the 12th International World Wide Web Conference (WWW 2003), Budapest, Hungary, May 20–24 2003. ACM Press.
@InProceedings{vosm03kaonserver,
author = "Raphael Volz and Daniel Oberle and Steffen Staab and Boris Motik",
title = "{KAON SERVER --- A Semantic Web Management System}",
booktitle = "Alternate Track Proc. of the 12th International World Wide Web Conference (WWW 2003)",
address = "Budapest, Hungary",
month = "May 20--24",
year = "2003",
publisher = "ACM Press",
}
The growing use of ontologies in applications creates the need for an infrastructure that allows developers to more easily combine different software modules like ontology stores, editors, or inference engines towards comprehensive ontology-based solutions. We call such an infrastructure Ontology Software Environment. The article discusses requirements and design issues of such an Ontology Software Environment. In particular, we present this discussion in light of the ontology and (meta)data standards that exist in the Semantic Web and present our corresponding implementation, the KAON SERVER.
Boris Motik, Alexander Maedche, and Raphael Volz. A Conceptual Modeling Approach for Semantics-Driven Enterprise Applications. In Robert Meersman and Zahir Tari, editors, Proc. of the 2002 Int. Conference on Ontologies, Databases and Applications of SEmantics (ODBASE 2002), volume 2519 of LNCS, pages 1082–1099, Irvine, CA, USA, 2002. Springer.
@InProceedings{mmv02conceptual,
author = "Boris Motik and Alexander Maedche and Raphael Volz",
title = "{A Conceptual Modeling Approach for Semantics-Driven Enterprise Applications}",
editor = "Robert Meersman and Zahir Tari",
booktitle = "Proc. of the 2002 Int. Conference on Ontologies, Databases and Applications of SEmantics (ODBASE 2002)",
address = "Irvine, CA, USA",
year = "2002",
publisher = "Springer",
series = "LNCS",
volume = "2519",
pages = "1082--1099",
}
In recent years ontologies – shared conceptualizations of some
domain – are increasingly seen as the key to further automation
of information processing. Although many approaches for
representing and applying ontologies have already been devised,
they haven't found their way into enterprise applications. In
this paper we argue that ontology-based systems lack critical
technical features, such as scalability, reliability, concurrency
and integration with existing data sources, as well as the
support for modularization and meta-concept modeling from the
conceptual modeling perspective. We present a conceptual modeling
approach that balances some of the trade-offs to more easily
integrate into existing enterprise information infrastructure.
Our approach is implemented within KAON, the Karlsruhe Ontology
and Semantic Web tool suite.
Erol Bozsak, Marc Ehrig, Siegfried Handschuh, Andreas Hotho, Alexander Maedche, Boris Motik, Daniel Oberle, Christoph Schmitz, Steffen Staab, Ljiljana Stojanovic, Nenad Stojanovic, Rudi Studer, Gerd Stumme, York Sure, Julien Tane, Raphael Volz, and Valentin Zacharias. KAON — Towards a Large Scale Semantic Web. In Kurt Bauknecht, A. Min Tjoa, and Gerald Quirchmayr, editors, Proc. of the 3rd Int. Conference on E-Commerce and Web Technologies (EC-Web 2002), volume 2455 of LNCS, pages 304–313, Aix-en-Provence, France, September 2–6 2002. Springer.
@InProceedings{behhmmossssssstvz02kaon2,
author = "Erol Bozsak and Marc Ehrig and Siegfried Handschuh and Andreas Hotho and Alexander Maedche and Boris Motik and Daniel Oberle and Christoph Schmitz and Steffen Staab and Ljiljana Stojanovic and Nenad Stojanovic and Rudi Studer and Gerd Stumme and York Sure and Julien Tane and Raphael Volz and Valentin Zacharias",
title = "{KAON --- Towards a Large Scale Semantic Web}",
editor = "Kurt Bauknecht and A. Min Tjoa and Gerald Quirchmayr",
booktitle = "Proc. of the 3rd Int. Conference on E-Commerce and Web Technologies (EC-Web 2002)",
address = "Aix-en-Provence, France",
month = "September 2--6",
year = "2002",
publisher = "Springer",
series = "LNCS",
volume = "2455",
pages = "304--313",
}
The Semantic Web will bring structure to the content of Web pages, being an extension of the currentWeb, in which information is given a well-defined meaning. Especially within e-commerce applications, SemanticWeb technologies in the form of ontologies and metadata are becoming increasingly prevalent and important. This paper introduce KAON - the Karlsruhe Ontology and Semantic WebTool Suite.KAONis developed jointly within several EU-funded projects and specifically designed to provide the ontology and metadata infrastructure needed for building, using and accessing semantics-driven applications on the Web and on your desktop.
Alexander Maedche, Boris Motik, Nuno Silva, and Raphael Volz. MAFRA — A MApping FRAmework for Distributed Ontologies. In Asunción Gómez-Pérez and Richard V. Benjamins, editors, Proc. of the 13th Int. Conference on Knowledge Engineering and Knowledge Management (EKAW 2002), volume 2473 of LNAI, pages 235–250, Siguenza, Spain, October 1–4 2002. Springer.
@InProceedings{mmsv02mafra,
author = "Alexander Maedche and Boris Motik and Nuno Silva and Raphael Volz",
title = "{MAFRA --- A MApping FRAmework for Distributed Ontologies}",
booktitle = "Proc. of the 13th Int. Conference on Knowledge Engineering and Knowledge Management (EKAW 2002)",
editor = "Asunci{\'o}n G{\'o}mez-P{\'e}rez and Richard V. Benjamins",
address = "Siguenza, Spain",
month = "October 1--4",
year = "2002",
publisher = "Springer",
series = "LNAI",
volume = "2473",
pages = "235--250",
}
Ontologies as means for conceptualizing and structuring domain
knowledge within a community of interest are seen as a key to
realize the Semantic Web vision. However, the decentralized nature
of the Web makes achieving this consensus across communities
difficult, thus, hampering efficient knowledge sharing between
them. In order to balance the autonomy of each community with the
need for interoperability, mapping mechanisms between distributed
ontologies in the Semantic Web are required. In this paper we
present MAFRA, an interactive, incremental and dynamic framework
for mapping distributed ontologies.
Ljiljana Stojanovic, Alexander Maedche, Boris Motik, and Nenad Stojanovic. User-Driven Ontology Evolution Management. In Asunción Gómez-Pérez and Richard V. Benjamins, editors, Proc. of the 13th Int. Conference on Knowledge Engineering and Knowledge Management (EKAW 2002), volume 2473 of LNAI, pages 285–300, Siguenza, Spain, October 1–4 2002. Springer.
@InProceedings{smms02userdriven,
author = "Ljiljana Stojanovic and Alexander Maedche and Boris Motik and Nenad Stojanovic",
title = "{User-Driven Ontology Evolution Management}",
booktitle = "Proc. of the 13th Int. Conference on Knowledge Engineering and Knowledge Management (EKAW 2002)",
editor = "Asunci{\'o}n G{\'o}mez-P{\'e}rez and Richard V. Benjamins",
address = "Siguenza, Spain",
month = "October 1--4",
year = "2002",
publisher = "Springer",
series = "LNAI",
volume = "2473",
pages = "285--300",
}
With rising importance of knowledge interchange, many industrial and academic applications have adopted ontologies as their conceptual backbone. However, industrial and academic environments are very dynamic, thus inducing changes to application requirements. To fulfill these changes, often the underlying ontology must be evolved as well. As ontologies grow in size, the complexity of change management increases, thus requiring a wellstructured ontology evolution process. In this paper we identify a possible sixphase evolution process and focus on providing the user with capabilities to control and customize it. We introduce the concept of an evolution strategy encapsulating policy for evolution with respect to user.s requirements.
Alexander Maedche, Boris Motik, Ljiljana Stojanovic, Rudi Studer, and Raphael Volz. Managing Multiple Ontologies and Ontology Evolution in Ontologging. In Mark A. Musen, Bernd Neumann, and Rudi Studer, editors, Proc. of the 17th Int. Federation for Information Processing Congress (IFIP 2002), volume 221 of IFIP Conference Proceedings, pages 51–63, Montréal, Québec, Canada, August 25–30 2002. Kluwer.
@InProceedings{mmssv02managing,
author = "Alexander Maedche and Boris Motik and Ljiljana Stojanovic and Rudi Studer and Raphael Volz",
title = "{Managing Multiple Ontologies and Ontology Evolution in Ontologging}",
editor = "Mark A. Musen and Bernd Neumann and Rudi Studer",
booktitle = "Proc. of the 17th Int. Federation for Information Processing Congress (IFIP 2002)",
address = "Montr{\'e}al, Qu{\'e}bec, Canada",
month = "August 25--30",
year = "2002",
publisher = "Kluwer",
series = "IFIP Conference Proceedings",
volume = "221",
pages = "51--63",
}
Ontologging is an ontology-driven environment to enable next generation knowledge management applications building on Semantic Web technology. In this paper we first present the conceptual architecture underlying Ontologging. Second, we focus on two important challenges for ontology-based knowledge management, namely the supporting multiple ontologies and managing ontology evolution. We will provide a general approach for handling these two essential issues within the Ontologging architecture.
Boris Motik and Vlado Glavinić. Enabling Agent Architecture through an RDF Query and Inference Engine. In Proc. of the 10th Mediterranean Electrotechnical Conference (MELECON 2000), volume II, pages 762–765, Lemesos, Cyprus, May 29–31 2000.
@InProceedings{mg00enabling,
author = "Boris Motik and Vlado Glavini{\'c}",
title = "{Enabling Agent Architecture through an RDF Query and Inference Engine}",
booktitle = "Proc. of the 10th Mediterranean Electrotechnical Conference (MELECON 2000)",
address = "Lemesos, Cyprus",
month = "May 29--31",
year = "2000",
volume = "II",
pages = "762--765",
}
Vlado Glavinić and Boris Motik. Agent-Oriented Information Retrieval and Processing. In Damir Kalpić and Vesna Hljuz-Dobrić, editors, Proc. 20th Int. Conference on Information Technology Interfaces (ITI '98), pages 163–168, Pula, Croatia, June 16–19 1998.
@InProceedings{gm98agentoriented,
author = "Vlado Glavini{\'c} and Boris Motik",
title = "{Agent-Oriented Information Retrieval and Processing}",
booktitle = "Proc. 20th Int. Conference on Information Technology Interfaces (ITI '98)",
editor = "Damir Kalpi{\'c} and Vesna Hljuz-Dobri{\'c}",
address = "Pula, Croatia",
month = "June 16--19",
year = "1998",
pages = "163--168",
}
Vlado Glavinić and Boris Motik. Object-Oriented Interface to MMS Services. In Proc. of the 9th Mediterranean Electrotechnical Conference (MELECON '98), volume II, pages 1375–1379, Tel-Aviv, Israel, May 18–20 1998.
@InProceedings{gm98objectoriented,
author = "Vlado Glavini{\'c} and Boris Motik",
title = "{Object-Oriented Interface to MMS Services}",
booktitle = "Proc. of the 9th Mediterranean Electrotechnical Conference (MELECON '98)",
address = "Tel-Aviv, Israel",
month = "May 18--20",
year = "1998",
volume = "II",
pages = "1375--1379",
}
Vlado Glavinić and Boris Motik. On PC-Based MMS Implementations. In Proc. of the 20th Int'l Convention Managing for Efficiency and Innovation (MIPRO '97), pages 193–196, Opatija, Croatia, May 19–23 1997.
@InProceedings{gm97pcbased,
author = "Vlado Glavini{\'c} and Boris Motik",
title = "{On PC-Based MMS Implementations}",
booktitle = "Proc. of the 20th Int'l Convention Managing for Efficiency and Innovation (MIPRO '97)",
address = "Opatija, Croatia",
month = "May 19--23",
year = "1997",
pages = "193--196",
}
Vlado Glavinić and Boris Motik. G-LOTOS Visual Development Environment. In Proc. of the 8th Mediterranean Electrotechnical Conference (MELECON '96), volume I, pages 136–139, Bari, Italy, May 13–16 1996.
@InProceedings{gm96g-lotos,
author = "Vlado Glavini{\'c} and Boris Motik",
title = "{G-LOTOS Visual Development Environment}",
booktitle = "Proc. of the 8th Mediterranean Electrotechnical Conference (MELECON '96)",
address = "Bari, Italy",
month = "May 13--16",
year = "1996",
volume = "I",
pages = "136--139",
}
Boris Motik and Vlado Glavinić. On Semantic Representation of LOTOS Programs. In Damir Kalpić and Vesna Hljuz-Dobrić, editors, Proc. 17th Int. Conference on Information Technology Interfaces (ITI '95), pages 217–224, Pula, Croatia, June 13–16 1995.
@InProceedings{mg95semantic,
author = "Boris Motik and Vlado Glavini{\'c}",
title = "{On Semantic Representation of LOTOS Programs}",
booktitle = "Proc. 17th Int. Conference on Information Technology Interfaces (ITI '95)",
editor = "Damir Kalpi{\'c} and Vesna Hljuz-Dobri{\'c}",
address = "Pula, Croatia",
month = "June 13--16",
year = "1995",
pages = "217--224",
}
In Workshops
František Simančík, Boris Motik, and Markus Krötzsch. Fixed Parameter Tractable Reasoning in DLs via Decomposition. In Riccardo Rosati, Sebastian Rudolph, and Michael Zakharyaschev, editors, Proc. of the 24rd Int. Workshop on Description Logics (DL 2011), volume 745 of CEUR Workshop Proceedings, Barcelona, Spain, July 13–16 2011.
@InProceedings{smk11dl-decomposition,
author = "Franti{\v{s}}ek Siman{\v{c}}{\'i}k and Boris Motik and Markus Kr{\"o}tzsch",
title = "{Fixed Parameter Tractable Reasoning in DLs via Decomposition}",
booktitle = "Proc. of the 24rd Int. Workshop on Description Logics (DL 2011)",
editor = "Riccardo Rosati and Sebastian Rudolph and Michael Zakharyaschev",
address = "Barcelona, Spain",
month = "July 13--16",
year = "2011",
series = "CEUR Workshop Proceedings",
volume = "745",
}
Birte Glimm, Ian Horrocks, and Boris Motik. Optimized DL Reasoning via Core Blocking. In Volker Haarslev, David Toman, and Grant Weddell, editors, Proc. of the 23rd Int. Workshop on Description Logics (DL 2010), volume 573 of CEUR Workshop Proceedings, Waterloo, ON, Canada, May 4–7 2010.
@InProceedings{ghm10core-blocking-DL,
author = "Birte Glimm and Ian Horrocks and Boris Motik",
title = "{Optimized DL Reasoning via Core Blocking}",
booktitle = "Proc. of the 23rd Int. Workshop on Description Logics (DL 2010)",
editor = "Volker Haarslev and David Toman and Grant Weddell",
address = "Waterloo, ON, Canada",
month = "May 4--7",
year = "2010",
series = "CEUR Workshop Proceedings",
volume = "573",
}
Héctor Pérez-Urbina, Ian Horrocks, and Boris Motik. Practical Aspects of Query Rewriting for OWL 2. In Rinke Hoekstra and Peter Patel-Schneider, editors, Proc. of the 5th Int. Workshop on OWL: Experiences and Directions (OWLED 2009), Chantilly, VA, USA, October 23–24 2009.
@InProceedings{puhm09practical-aspects,
author = "H{\'e}ctor P{\'e}rez-Urbina and Ian Horrocks and Boris Motik",
title = "{Practical Aspects of Query Rewriting for OWL 2}",
booktitle = "Proc. of the 5th Int. Workshop on OWL: Experiences and Directions (OWLED 2009)",
editor = "Rinke Hoekstra and Peter Patel-Schneider",
address = "Chantilly, VA, USA",
month = "October 23--24",
year = "2009",
}
Query answering for the QL profile of OWL 2 and a substantial fragment of the EL profile can be implemented via query rewriting: a query posed over an ontology is first rewritten using the conceptual part of the ontology and then the evaluation of the rewritten query is delegated to a (deductive) database where the instance data resides. In our previous work we presented a rewriting algorithm for OWL QL that can also deal with most of the QL profile. In order to test the likely practicality of our rewriting algorithm, we have implemented it in a query rewriting system that we call REQUIEM. A recent empirical evaluation of REQUIEM, in which we considered OWL 2 QL ontologies, indicates that it produces significantly smaller rewritings than existing approaches in most cases. However, our results suggest that typical queries over realistic ontologies can still lead to very large rewritings (e.g., containing many thousands of queries). In this paper, we describe query rewriting, briefly present the results of our evaluation, and discuss various optimization techniques aimed at reducing the size of the rewritings. Moreover, we present some preliminary results from an ongoing empirical evaluation of REQUIEM in which we consider OWL 2 EL ontologies.
Bernardo Cuenca Grau and Boris Motik. Importing Ontologies with Hidden Content. In Bernardo Cuenca Grau, Ian Horrocks, Boris Motik, and Ulrike Sattler, editors, Proc. of the 22nd Int. Workshop on Description Logics (DL 2009), volume 477 of CEUR Workshop Proceedings, Oxford, UK, July 27–30 2009.
@InProceedings{gm09ibq-EL,
author = "Bernardo Cuenca Grau and Boris Motik",
title = "{Importing Ontologies with Hidden Content}",
booktitle = "Proc. of the 22nd Int. Workshop on Description Logics (DL 2009)",
editor = "Bernardo Cuenca Grau and Ian Horrocks and Boris Motik and Ulrike Sattler",
address = "Oxford, UK",
month = "July 27--30",
year = "2009",
series = "CEUR Workshop Proceedings",
volume = "477",
}
Rob Shearer, Ian Horrocks, and Boris Motik. Exploiting Partial Information in Taxonomy Construction. In Bernardo Cuenca Grau, Ian Horrocks, Boris Motik, and Ulrike Sattler, editors, Proc. of the 22nd Int. Workshop on Description Logics (DL 2009), volume 477 of CEUR Workshop Proceedings, Oxford, UK, July 27–30 2009.
@InProceedings{shm09partial-information,
author = "Rob Shearer and Ian Horrocks and Boris Motik",
title = "{Exploiting Partial Information in Taxonomy Construction}",
booktitle = "Proc. of the 22nd Int. Workshop on Description Logics (DL 2009)",
editor = "Bernardo Cuenca Grau and Ian Horrocks and Boris Motik and Ulrike Sattler",
address = "Oxford, UK",
month = "July 27--30",
year = "2009",
series = "CEUR Workshop Proceedings",
volume = "477",
}
Héctor Pérez-Urbina, Boris Motik, and Ian Horrocks. A Comparison of Query Rewriting Techniques for DL-lite. In Bernardo Cuenca Grau, Ian Horrocks, Boris Motik, and Ulrike Sattler, editors, Proc. of the 22nd Int. Workshop on Description Logics (DL 2009), volume 477 of CEUR Workshop Proceedings, Oxford, UK, July 27–30 2009.
@InProceedings{pumh09comparison,
author = "H{\'e}ctor P{\'e}rez-Urbina and Boris Motik and Ian Horrocks",
title = "{A Comparison of Query Rewriting Techniques for DL-lite}",
booktitle = "Proc. of the 22nd Int. Workshop on Description Logics (DL 2009)",
editor = "Bernardo Cuenca Grau and Ian Horrocks and Boris Motik and Ulrike Sattler",
address = "Oxford, UK",
month = "July 27--30",
year = "2009",
series = "CEUR Workshop Proceedings",
volume = "477",
}
Boris Motik, Bernardo Cuenca Grau, Ian Horrocks, and Ulrike Sattler. Modeling Ontologies Using OWL, Description Graphs, and Rules. In Alan Ruttenberg, Ulrile Sattler, and Cathy Dolbear, editors, Proc. of the 5th Int. Workshop on OWL: Experiences and Directions (OWLED 2008 EU), Karlsruhe, Germany, October 26–27 2008.
@InProceedings{mcghs2008graphs,
author = "Boris Motik and Bernardo Cuenca Grau and Ian Horrocks and Ulrike Sattler",
title = "{Modeling Ontologies Using OWL, Description Graphs, and Rules}",
booktitle = "Proc. of the 5th Int. Workshop on OWL: Experiences and Directions (OWLED 2008 EU)",
editor = "Alan Ruttenberg and Ulrile Sattler and Cathy Dolbear",
address = "Karlsruhe, Germany",
month = "October 26--27",
year = "2008",
}
Rob Shearer, Boris Motik, and Ian Horrocks. HermiT: A Highly-Efficient OWL Reasoner. In Alan Ruttenberg, Ulrile Sattler, and Cathy Dolbear, editors, Proc. of the 5th Int. Workshop on OWL: Experiences and Directions (OWLED 2008 EU), Karlsruhe, Germany, October 26–27 2008.
@InProceedings{smh08HermiT,
author = "Rob Shearer and Boris Motik and Ian Horrocks",
title = "{HermiT: A Highly-Efficient OWL Reasoner}",
booktitle = "Proc. of the 5th Int. Workshop on OWL: Experiences and Directions (OWLED 2008 EU)",
editor = "Alan Ruttenberg and Ulrile Sattler and Cathy Dolbear",
address = "Karlsruhe, Germany",
month = "October 26--27",
year = "2008",
}
%!TEX root = paper.tex
HermiT is a new OWL reasoner based on a novel "hypertableau'' calculus. The
new calculus addresses performance problems due to nondeterminism and model
size—the primary sources of complexity in state-of-the-art OWL reasoners.
The latter is particularly important in practice, and it is achieved in HermiT
with an improved blocking strategy and and an optimization that tries to reuse
existing individuals rather than generating new ones. HermiT also incorporates
a number of other novel optimizations, such as a more efficient approach to
handling nominals, and various techniques for optimizing ontology
classification. Our tests show that HermiT is usually much faster than other
reasoners when classifying complex ontologies, and it is already able to
classify a number of ontologies which no other reasoner has been able to
handle.
Boris Motik, Rob Shearer, and Ian Horrocks. Optimizing the Nominal Introduction Rule in (Hyper)Tableau Calculi. In Franz Baader, Carsten Lutz, and Boris Motik, editors, Proc. of the 21st Int. Workshop on Description Logics (DL 2008), volume 353 of CEUR Workshop Proceedings, Dresden, Germany, May 13–16 2008.
@InProceedings{msh08rewriting,
author = "Boris Motik and Rob Shearer and Ian Horrocks",
title = "{Optimizing the Nominal Introduction Rule in (Hyper)Tableau Calculi}",
booktitle = "Proc. of the 21st Int. Workshop on Description Logics (DL 2008)",
editor = "Franz Baader and Carsten Lutz and Boris Motik",
address = "Dresden, Germany",
month = "May 13--16",
year = "2008",
series = "CEUR Workshop Proceedings",
volume = "353",
}
%!TEX root = paper.tex
Interactions between nominals, inverse roles, and number restrictions provide
challenges to description logic reasoners, as they can make models of a
knowledge base non-forest-like. The solution to this problem used by the
standard tableau calculus can incur a high degree of nondeterminism and can
lead to the generation of unnecessarily large models. We present a more
efficient approach to handling this combination of constructs. We use this
approach to extend our hypertableau calculus to SHOIQ. This approach,
however, is equally applicable to traditional tableau calculi.
Boris Motik, Bernardo Cuenca Grau, and Ulrike Sattler. The Representation of Structured Objects in DLs using Description Graphs. In Franz Baader, Carsten Lutz, and Boris Motik, editors, Proc. of the 21st Int. Workshop on Description Logics (DL 2008), volume 353 of CEUR Workshop Proceedings, Dresden, Germany, May 13–16 2008.
@InProceedings{mgs08description-graphs,
author = "Boris Motik and Bernardo Cuenca Grau and Ulrike Sattler",
title = "{The Representation of Structured Objects in DLs using Description Graphs}",
booktitle = "Proc. of the 21st Int. Workshop on Description Logics (DL 2008)",
editor = "Franz Baader and Carsten Lutz and Boris Motik",
address = "Dresden, Germany",
month = "May 13--16",
year = "2008",
series = "CEUR Workshop Proceedings",
volume = "353",
}
Héctor Pérez-Urbina, Boris Motik, and Ian Horrocks. Rewriting Conjunctive Queries under Description Logic Constraints. In Andrea Cal`{i}, Georg Gottlob, Laks V.S. Lakshmanan, and Davide Martinenghi, editors, Proc. of the Int. Workshop on Logic in Databases (LID 2008), Rome, Italy, May 19–20 2008.
@InProceedings{pumh08rewriting-ELHI,
author = "H{\'e}ctor P{\'e}rez-Urbina and Boris Motik and Ian Horrocks",
title = "{Rewriting Conjunctive Queries under Description Logic Constraints}",
booktitle = "Proc. of the Int. Workshop on Logic in Databases (LID 2008)",
editor = "Andrea Cal`{i} and Georg Gottlob and Laks V.S. Lakshmanan and Davide Martinenghi",
address = "Rome, Italy",
month = "May 19--20",
year = "2008",
}
We consider the problems of conjunctive query answering and rewriting under Description Logic constraints. We present a query rewriting algorithm for $\ELHI$ knowledge bases, and use it to show that query answering in this setting is
PTime-complete w.r.t. data complexity. We show that our algorithm is worst-case optimal for languages with data complexity of query answering ranging from \LogSpace to PTime-complete.
Héctor Pérez-Urbina, Boris Motik, and Ian Horrocks. Rewriting Conjunctive Queries over Description Logic Knowledge Bases. In Klaus-Dieter Schewe and Bernhard Thalheim, editors, Proc. of the Int. Workshop on Semantics in Data and Knowledge Bases (SDKB 2008), volume 4925 of LNCS, pages 199–214, Nantes, France, March 29 2008. Springer.
@InProceedings{pumh08rewriting-DLlite-plus,
author = "H{\'e}ctor P{\'e}rez-Urbina and Boris Motik and Ian Horrocks",
title = "{Rewriting Conjunctive Queries over Description Logic Knowledge Bases}",
booktitle = "Proc. of the Int. Workshop on Semantics in Data and Knowledge Bases (SDKB 2008)",
editor = "Klaus-Dieter Schewe and Bernhard Thalheim",
address = "Nantes, France",
month = "March 29",
year = "2008",
publisher = "Springer",
series = "LNCS",
volume = "4925",
pages = "199--214",
}
We consider the problems of conjunctive query answering and
rewriting for information integration systems in which a Description
Logic ontology is used to provide a global view of the data. We
present a resolution-based query rewriting algorithm for
$\DLlitePlus$ ontologies, and use it to show that query answering in
this setting is \NLogSpace-complete with respect to data complexity.
We also show that our algorithm produces an optimal rewriting when
the input ontology is expressed in the language $\DLlite$. Finally,
we sketch an extended version of the algorithm that would, we are
confident, be optimal for several DL languages with data complexity
of query answering ranging from \LogSpace to
PTime-complete.
Boris Motik, Rob Shearer, and Ian Horrocks. A Hypertableau Calculus for SHIQ. In Diego Calvanese, Enriso Franconi, Volker Haarslev, Domenico Lembo, Boris Motik, Sergio Tessaris, and Anny-Yasmin Turhan, editors, Proc. of the 20th Int. Workshop on Description Logics (DL 2007), pages 419–426, Brixen/Bressanone, Italy, June 8–10 2007. Bozen/Bolzano University Press.
@InProceedings{msh07hypertableau,
author = "Boris Motik and Rob Shearer and Ian Horrocks",
title = "{A Hypertableau Calculus for SHIQ}",
booktitle = "Proc. of the 20th Int. Workshop on Description Logics (DL 2007)",
editor = "Diego Calvanese and Enriso Franconi and Volker Haarslev and Domenico Lembo and Boris Motik and Sergio Tessaris and Anny-Yasmin Turhan",
address = "Brixen/Bressanone, Italy",
month = "June 8--10",
year = "2007",
publisher = "Bozen/Bolzano University Press",
pages = "419--426",
}
We present a novel reasoning calculus for the Description Logic
SHIQ. In order to reduce the nondeterminism due to general
inclusion axioms, we base our calculus on hypertableau and
hyperresolution calculi, which we extend with a blocking condition
to ensure termination. To prevent the calculus from generating large
models, we introduce "anywhere'' pairwise blocking. Our
preliminary implementation shows significant performance
improvements on several well-known ontologies. To the best of our
knowledge, our reasoner is currently the only one that can classify
the original version of the GALEN terminology.
Boris Motik, Ian Horrocks, and Ulrike Sattler. Adding Integrity Constraints to OWL. In Christine Golbreich, Aditya Kalyanpur, and Bijan Parsia, editors, OWL: Experiences and Directions 2007 (OWLED 2007), Innsbruck, Austria, June 6–7 2007.
@InProceedings{mhs07adding-constraints,
author = "Boris Motik and Ian Horrocks and Ulrike Sattler",
title = "{Adding Integrity Constraints to OWL}",
booktitle = "OWL: Experiences and Directions 2007 (OWLED 2007)",
editor = "Christine Golbreich and Aditya Kalyanpur and Bijan Parsia",
address = "Innsbruck, Austria",
month = "June 6--7",
year = "2007",
}
Schema statements in OWL are interpreted quite differently from
analogous statements in relational databases. If these statements
are meant to be interpreted as integrity constraints (ICs), OWL's
interpretation may seem confusing and/or inappropriate. Therefore,
we propose an extension of OWL with ICs that captures the intuition
behind ICs in relational databases. We show that, if the constraints
are satisfied, we can disregard them while answering a broad range
of positive queries.
Boris Motik and Ian Horrocks. Problems with OWL Syntax. In Bernardo Cuenca Grau, Pascal Hitzler, Connor Shankey, and Evan Wallace, editors, OWL: Experiences and Directions 2006 (OWLED 2006), Athens, GA, USA, November 10–11 2006.
@InProceedings{mh06problems-owl,
author = "Boris Motik and Ian Horrocks",
title = "{Problems with OWL Syntax}",
booktitle = "OWL: Experiences and Directions 2006 (OWLED 2006)",
editor = "Bernardo Cuenca Grau and Pascal Hitzler and Connor Shankey and Evan Wallace",
address = "Athens, GA, USA",
month = "November 10--11",
year = "2006",
}
In this paper we discuss three problems with OWL syntax that
repeatedly surface in practice. The first problem is that OWL does
not allow for explicit declarations—assertions that a
certain class, property, or an individual exists in an ontology.
This aspect of the OWL standard was often misinterpreted, which
caused design errors in OWL APIs; moreover, the lack of declarations
makes devising an intuitive structural consistency check for OWL
ontologies difficult. The second problem is that OWL Abstract Syntax
and OWL RDF syntax rely on the separation between object and data
property names for disambiguation. We show that this prevents an
unambiguous interpretation of certain syntactically well-formed OWL
ontologies; furthermore, it makes implementing OWL parsers
unnecessarily difficult. The third problem is that OWL Abstract
Syntax cannot be translated into OWL RDF syntax without loss of
information. We present possible solutions to these three problems,
which, if adopted in OWL 1.1, would lead to a cleaner standard and
would significantly simplify the implementation of OWL APIs.
Boris Motik. Description Logics and Disjunctive Datalog—More Than just a Fleeting Resemblance? In Holger Schlingloff, editor, Proc. of the 4th Workshop on Methods for Modalities (M4M-4), volume 194 of Informatik-Berichte der Humboldt-Universität zu Berlin, pages 246–265, Berlin, Germany, December 1–2 2005.
@InProceedings{m05dl-and-dd,
author = "Boris Motik",
title = "{Description Logics and Disjunctive Datalog---More Than just a Fleeting Resemblance?}",
booktitle = "Proc. of the 4th Workshop on Methods for Modalities (M4M-4)",
editor = "Holger Schlingloff",
address = "Berlin, Germany",
month = "December 1--2",
year = "2005",
series = "Informatik-Berichte der Humboldt-Universit{\"a}t zu Berlin",
volume = "194",
pages = "246--265",
}
As applications of description logics (DLs) proliferate, efficient
reasoning with large ABoxes (sets of individuals with descriptions)
becomes ever more important. Motivated by the prospects of reusing
optimization techniques of deductive databases, we developed a novel
algorithm for reasoning in description logic, which reduces a DL
knowledge base to a disjunctive datalog program without changing the
set of relevant consequences. This allows to answer queries by
applying optimization techniques, such as join-order optimizations
or magic sets. The algorithm supports the very expressive logic
SHIQD, so the reduction is quite technically involved. In this
paper we present a simplified algorithm for the basic logic \ALC.
Whereas this algorithm is much easier to understand, it is based on
the same principles as the general one.
Stephan Grimm and Boris Motik. Closed World Reasoning in the Semantic Web through Epistemic Operators. In Bernardo Cuenca Grau, Ian Horrocks, Bijan Parsia, and Peter Patel-Schneider, editors, Proc. of the Workshop on OWL: Experiences and Directions (OWLED 2005), Galway, Ireland, November 11–12 2005.
@InProceedings{gm05closed,
author = "Stephan Grimm and Boris Motik",
title = "{Closed World Reasoning in the Semantic Web through Epistemic Operators}",
booktitle = "Proc. of the Workshop on OWL: Experiences and Directions (OWLED 2005)",
editor = "Bernardo Cuenca Grau and Ian Horrocks and Bijan Parsia and Peter Patel-Schneider",
address = "Galway, Ireland",
month = "November 11--12",
year = "2005",
}
Peter Haase and Boris Motik. A Mapping System for the Integration of OWL-DL Ontologies. In Axel Hahn, Sven Abels, and Liane Haak, editors, Proc. of the 1st Int. ACM Workshop on Interoperability of Heterogeneous Information Systems (IHIS'05), pages 9–16, Bremen, Germany, November 4 2005. ACM Press.
@InProceedings{hm05mapping,
author = "Peter Haase and Boris Motik",
title = "{A Mapping System for the Integration of OWL-DL Ontologies}",
booktitle = "Proc. of the 1st Int. ACM Workshop on Interoperability of Heterogeneous Information Systems (IHIS'05)",
editor = "Axel Hahn and Sven Abels and Liane Haak",
address = "Bremen, Germany",
month = "November 4",
publisher = "ACM Press",
year = "2005",
pages = "9--16",
}
To enable interoperability between applications in
distributed information systems based
on heterogeneous ontologies, it is necessary to formally define the
notion of a mapping between ontologies.
In this paper, we define a mapping system for OWL-DL ontologies, where mappings are expressed as correspondences between conjunctive queries over ontologies.
As query answering within
such a general mapping system is undecidable, we identify a decidable fragment of the mapping system, which corresponds to OWL-DL extended with DL-safe rules.
We further show how the mapping system can be applied for the task of ontology integration and present a query answering algorithm.
Ullrich Hustadt and Boris Motik. Description Logics and Disjunctive Datalog—The Story so Far. In Ian Horrocks, Ulrike Sattler, and Frank Wolter, editors, Proc. of the 2005 Int. Workshop on Description Logics (DL 2005), volume 147 of CEUR Workshop Proceedings, Edinburgh, UK, July 26–28 2005.
@InProceedings{hm05dl-dd-so-far,
author = "Ullrich Hustadt and Boris Motik",
title = "{Description Logics and Disjunctive Datalog---The Story so Far}",
booktitle = "Proc. of the 2005 Int. Workshop on Description Logics (DL 2005)",
editor = "Ian Horrocks and Ulrike Sattler and Frank Wolter",
address = "Edinburgh, UK",
month = "July 26--28",
year = "2005",
series = "CEUR Workshop Proceedings",
volume = "147",
}
In this paper we present an overview of our recent work on the
relationship between description logics and disjunctive datalog. In
particular, we reduce satisfiability and instance checking in SHIQ
to corresponding problems in disjunctive datalog. This allows us to
apply practically successful deductive database optimization
techniques, such as magic sets. Interestingly, the reduction also
allows us to obtain novel theoretical results on description logics.
In particular, we show that the data complexity of reasoning
in SHIQ is in
NP, and we define a fragment called Horn-SHIQ for
which the data complexity is in P. Finally, the reduction provides
a basis for query answering in an extension of SHIQ with so-called
DL-safe rules.
Pascal Hitzler, Jürgen Angele, Boris Motik, and Rudi Studer. Bridging the Paradigm Gap with Rules for OWL. In Proc. of the W3C Workshop on Rule Languages for Interoperability, Washington, DC, USA, April 27–28 2005.
@InProceedings{hams05bridging,
author = "Pascal Hitzler and J{\"u}rgen Angele and Boris Motik and Rudi Studer",
title = "{Bridging the Paradigm Gap with Rules for OWL}",
booktitle = "Proc. of the W3C Workshop on Rule Languages for Interoperability",
address = "Washington, DC, USA",
month = "April 27--28",
year = "2005",
}
Stephan Grimm, Boris Motik, and Chris Preist. Variance in e-Business Service Discovery. In David Martin, Rubén Lara, and Takahira Yamaguchi, editors, Proc. of the ISWC 2004 Workshop on Semantic Web Services: Preparing to Meet the World of Business Applications, volume 119 of CEUR Workshop Proceedings, Hiroshima, Japan, November 8 2004.
@InProceedings{gmp04variance,
author = "Stephan Grimm and Boris Motik and Chris Preist",
title = "{Variance in e-Business Service Discovery}",
booktitle = "Proc. of the ISWC 2004 Workshop on Semantic Web Services: Preparing to Meet the World of Business Applications",
editor = "David Martin and Rub{\'e}n Lara and Takahira Yamaguchi",
address = "Hiroshima, Japan",
month = "November 8",
year = "2004",
series = "CEUR Workshop Proceedings",
volume = "119",
}
Automating the process of B2B partner discovery and contract
negotiation is expected to significantly optimise company processes.
Numerous existing proposals for discovery follow the approach where
service descriptions are expressed by concept expressions in
description logics (DL), and description matching is performed by
well-known DL inferences. However, these approaches do not always
produce results one might intuitively expect, due to a gap between
the formal semantics of service descriptions and human intuition. In
this paper, we address this problem by analysing the connection
between the modeler's intuition and formal logic used to
operationalise discovery. Furthermore, we show how to correctly map
the intuition into description logic constructs. Finally, we
investigate different inferences used to realise service discovery.
Boris Motik, Alexander Maedche, and Raphael Volz. Optimizing Query Answering in Description Logics using Disjunctive Deductive Databases. In François Bry, Carsten Lutz, Ulrike Sattler, and Mareike Schoop, editors, Proc. of the 10th Int. Workshop on Knowledge Representation meets Databases (KRDB 2003), volume 79 of CEUR Workshop Proceedings, Hamburg, Germany, September 15–16 2003.
@InProceedings{mmv03optimizing,
author = "Boris Motik and Alexander Maedche and Raphael Volz",
title = "{Optimizing Query Answering in Description Logics using Disjunctive Deductive Databases}",
booktitle = "Proc. of the 10th Int. Workshop on Knowledge Representation meets Databases (KRDB 2003)",
editor = "Fran\c{c}ois Bry and Carsten Lutz and Ulrike Sattler and Mareike Schoop",
address = "Hamburg, Germany",
month = "September 15--16",
year = "2003",
series = "CEUR Workshop Proceedings",
volume = "79",
}
Motivated by the possibilities of applying deductive database
technology for efficient query answering in description logics, we
present a translation operator $\mu$ that transforms non-recursive
ALC ontologies into a disjunctive deductive database. Contrary
to our previous work, in this paper we focus on handling negation,
disjunction and existential quantifiers, which cannot be handled
by deductive databases in a straightforward manner. We present a
performance evaluation of our approach, confirming the intuition
that techniques for optimizing query answering in disjunctive
deductive databases may improve query answering in description
logics.
Raphael Volz, Steffen Staab, and Boris Motik. Incremental Maintenance of Dynamic Datalog Programs. In Raphael Volz, Stefan Decker, and Isabel F. Cruz, editors, Proc. of the 1st Int. Workshop on Practical and Scalable Semantic Systems (PSSS1), volume 89 of CEUR Workshop Proceedings, Sanibel Island, FL, USA, October 20 2003.
@InProceedings{vsm03incremental-ws,
author = "Raphael Volz and Steffen Staab and Boris Motik",
title = "{Incremental Maintenance of Dynamic Datalog Programs}",
editor = "Raphael Volz and Stefan Decker and Isabel F. Cruz",
booktitle = "Proc. of the 1st Int. Workshop on Practical and Scalable Semantic Systems (PSSS1)",
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month = "October 20",
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Alexander Maedche, Boris Motik, Nuno Silva, and Raphael Volz. MAFRA — An Ontology MApping FRAmework in the context of the Semantic Web. In Proc. of the ECAI 2002 Workshop on Knowledge Transformation for the Semantic Web (KTSW), Lyon, France, July 23 2002.
@InProceedings{mmsv02mafra-ws,
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title = "{MAFRA --- An Ontology MApping FRAmework in the context of the Semantic Web}",
booktitle = "Proc. of the ECAI 2002 Workshop on Knowledge Transformation for the Semantic Web (KTSW)",
address = "Lyon, France",
month = "July 23",
year = "2002",
}
Ontologies as means for conceptualizing and structuring domain
knowledge within a community of interest are seen as a key to
realize the Semantic Web vision. However, the decentralized nature
of the Web makes achieving this consensus across communities
difficult, thus, hampering efficient knowledge sharing between
them. In order to balance the autonomy of each community with the
need for interoperability, mapping mechanisms between distributed
ontologies in the Semantic Web are required. In this paper we
present MAFRA, an interactive, incremental and dynamic framework
for mapping distributed ontologies in the Semantic Web.
Book Contributions
Boris Motik. Resolution-Based Reasoning for Ontologies, 2nd edition. In Steffen Staab and Rudi Studer, editors, Handbook on Ontologies, International Handbooks on Information Systems, pages 529–550, 2009. Springer.
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We overview the algorithms for reasoning with description logic (DL)
ontologies based on resolution. These algorithms often have
worst-case optimal complexity, and, by relying on vast experience in
building resolution theorem provers, they can be implemented
efficiently. Furthermore, we present a resolution-based algorithm
that reduces a DL knowledge base into a disjunctive datalog program,
while preserving the set of entailed facts. This reduction enables
the application of optimization techniques from deductive databases,
such as magic sets, to reasoning in DLs. This approach has proven
itself in practice on ontologies with relatively small and simple
TBoxes, but large ABoxes.
Boris Motik, Alexander Maedche, and Raphael Volz. Ontology Representation and Querying for Realizing Semantics-Driven Applications. In Giorgos Samou and Stefanos Kollias, editors, Multimedia Content and the Semantic Web: Methods, Standards and Tools, pages 45–73, 2005. John Wiley & Sons.
@InCollection{mmv05ontology-representation,
author = "Boris Motik and Alexander Maedche and Raphael Volz",
title = "{Ontology Representation and Querying for Realizing Semantics-Driven Applications}",
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In recent years ontologies – shared conceptualizations of some
domain – are increasingly seen as the key to further advances in
automation of information processing. Although many approaches for
representing and querying ontologies have already been devised,
they haven't found their way into enterprise applications yet.
Many of them offer a high degree of expressivity, but require
complicated reasoning and query answering procedures, and often
lack features needed in practical applications, such as
constraints and meta-concept modeling. This is compounded by the
lack of critical technical features in ontology management tools,
such as scalability, reliability, concurrency and the support for
ontology modularization. We present an approach for ontology
representation and querying that balances some of the trade-offs
to more easily integrate into existing enterprise information
infrastructure. In particular, we focus on efficient evaluation of
queries using existing information management infrastructure, such
as relational databases. Finally, we describe a prototype
implementation within KAON, the Karlsruhe Ontology and Semantic
Web tool suite.
Daniel Oberle, Raphael Volz, Steffen Staab, and Boris Motik. An Extensible Ontology Software Environment. In Steffen Staab and Rudi Studer, editors, Handbook on Ontologies, International Handbooks on Information Systems, pages 299–320, 2004. Springer.
@InCollection{ovsm04extensible,
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publisher = "Springer",
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The growing use of ontologies in applications creates the need for an infrastructure that allows developers to more easily combine different software modules like ontology stores, editors, or inference engines towards comprehensive ontology-based solutions. We call such an infrastructure Ontology Software Environment. The article discusses requirements and design issues of such an Ontology Software Environment. In particular, we present this discussion in light of the ontology and (meta)data standards that exist in the Semantic Web and present our corresponding implementation, the KAON SERVER.
Technical Reports
Boris Motik, Bernardo Cuenca Grau, and Ulrike Sattler. Structured Objects in OWL: Representation and Reasoning. Technical Report, University of Oxford, UK, 2007.
@TechReport{mgs07structured-objects-report,
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Applications of semantic technologies often require the
representation of and reasoning with structured
objects—that is, objects composed of parts connected in complex
ways. Although OWL is a general and powerful language, its class
descriptions and axioms cannot be used to describe arbitrarily
connected structures. An OWL representation of structured objects
can thus be underconstrained, which reduces the inferences that can
be drawn and causes performance problems in reasoning. To address
these problems, we extend OWL with description graphs, which
allow for the description of structured objects in a simple and
precise way. To represent conditional aspects of the domain, we also
allow for SWRL-like rules over description graphs. Based on an
observation about the nature of structured objects, we ensure
decidability of our formalism. We also present a hypertableau-based
decision procedure, which we implemented in the HermiT reasoner. To
evaluate its performance, we have extracted description graphs from
the GALEN and FMA ontologies, classified them successfully, and even
detected a modeling error in GALEN.
Boris Motik, Ian Horrocks, and Ulrike Sattler. Integrating Description Logics and Relational Databases. Technical Report, University of Manchester, UK, 2006.
@TechReport{mhs06constraints-report,
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In this paper, we compare description logics with relational
databases with respect to their treatment of schema constraints, the
languages used to express these constraints, and the approaches to
query answering and constraint checking. Our analysis reveals a
significant overlap between the two formalisms. Inspired by the
integrity constraints of relational databases, we define a notion of
integrity constraints for description logics. We analyze different
possibilities for defining the semantics of the constraints.
Finally, we present several algorithms for checking constraint
satisfaction for description logics with varying degrees of
expressivity.
Boris Motik and Riccardo Rosati. Closing Semantic Web Ontologies. Technical Report, University of Manchester, UK, 2006.
@TechReport{mr06closing-report,
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title = "{Closing Semantic Web Ontologies}",
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In this paper, we present a novel formalism of hybrid MKNF
knowledge bases, which allows us to seamlessly integrate an arbitrary
decidable description logic with logic programming rules. We thus
obtain a powerful hybrid formalism that combines the best features
of both description logics, such as the ability to model taxonomic
knowledge, and logic programming, such as the ability to perform
nonmonotonic reasoning. Extending DLs with unrestricted rules makes
reasoning undecidable. To obtain decidability, we apply the
well-known DL-safety restriction that makes the rules
applicable only to explicitly named individuals, and thus trade some
expressivity for decidability. We present several reasoning
algorithms for different fragments of our logic, as well as the
corresponding complexity results. Our results show that, in many
cases, the data complexity of reasoning with hybrid MKNF knowledge
bases is not higher than the data complexity of reasoning in the
corresponding fragment of logic programming.
Ullrich Hustadt, Boris Motik, and Ulrike Sattler. Reasoning for Description Logics around SHIQ in a Resolution Framework. Technical Report 3-8-04/04, FZI, Germany, 2004.
@TechReport{hms04reasoning-report,
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Ullrich Hustadt, Boris Motik, and Ulrike Sattler. Reducing SHIQ- Description Logics to Disjunctive Datalog Programs. Technical Report 1-8-11/03, FZI, Germany, 2004.
@TechReport{hms04reducing-report,
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number = "1-8-11/03",
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}
Proceedings
Bernardo Cuenca Grau, Ian Horrocks, Boris Motik, and Ulrike Sattler, editors. Proceedings of the 22nd International Workshop on Description Logics (DL 2009). Oxford, UK, July 27–30 2009. CEUR Workshop Proceedings. Vol. 477.
@Proceedings{dl09,
title = "{Proceedings of the 22nd International Workshop on Description Logics (DL 2009)}",
editor = "Bernardo Cuenca Grau and Ian Horrocks and Boris Motik and Ulrike Sattler",
address = "Oxford, UK",
month = "July 27--30",
year = "2009",
publisher = "CEUR Workshop Proceedings",
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}
Franz Baader, Carsten Lutz, and Boris Motik, editors. Proceedings of the 21st International Workshop on Description Logics (DL 2008). Dresden, Germany, May 13–16 2008. CEUR Workshop Proceedings. Vol. 353.
@Proceedings{dl08,
title = "{Proceedings of the 21st International Workshop on Description Logics (DL 2008)}",
editor = "Franz Baader and Carsten Lutz and Boris Motik",
address = "Dresden, Germany",
month = "May 13--16",
year = "2008",
publisher = "CEUR Workshop Proceedings",
note = "Vol. 353",
}
Diego Calvanese, Enrico Franconi, Volker Haarslev, Domenico Lembo, Boris Motik, Sergio Tessaris, and Anni-Yasmin Turhan, editors. Proceedings of the 20th International Workshop on Description Logics (DL 2007). Brixen/Bressanone, Italy, June 8–10 2007. CEUR Workshop Proceedings. Vol. 250.
@Proceedings{dl07,
title = "{Proceedings of the 20th International Workshop on Description Logics (DL 2007)}",
editor = "Diego Calvanese and Enrico Franconi and Volker Haarslev and Domenico Lembo and Boris Motik and Sergio Tessaris and Anni-Yasmin Turhan",
address = "Brixen/Bressanone, Italy",
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year = "2007",
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Books
Boris Motik and Julijan Šribar. C++ Demystified. Element, Zagreb, Croatia, 2nd edition, 2001. In Croatian.
@Book{demistificirani1,
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publisher = "Element",
year = "2001",
note = "In Croatian",
}
@Book{demistificirani2,
author = "Boris Motik and Julijan {\v{S}}ribar",
title = "{C++ Demystified}",
address = "Zagreb, Croatia",
publisher = "Element",
year = "1997",
note = "In Croatian",
}
Theses
Boris Motik. Reasoning in Description Logics using Resolution and Deductive Databases. PhD Thesis, Univesität Karlsruhe (TH), Karlsruhe, Germany, January 2006.
@PhDThesis{motik06PhD,
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title = "{Reasoning in Description Logics using Resolution and Deductive Databases}",
school = "Univesit{\"a}t Karlsruhe (TH), Karlsruhe, Germany",
month = "January",
year = "2006",
}
Boris Motik. Improving Interaction with the Information Infrastructure Using Intelligent Agents. Master's Thesis, Faculty of Electrical Engineering and Computing, University of Zagreb, Croatia, December 1999. In Croatian.
@MastersThesis{motik99masters,
author = "Boris Motik",
title = "{Improving Interaction with the Information Infrastructure Using Intelligent Agents}",
school = "Faculty of Electrical Engineering and Computing, University of Zagreb, Croatia",
month = "December",
year = "1999",
note = "In Croatian",
}
Boris Motik. Integrated Development Environment for Specifying Distributed Systems. Diploma Thesis, Faculty of Electrical Engineering and Computing, University of Zagreb, Croatia, February 1996. In Croatian.
@MastersThesis{motik96diploma,
author = "Boris Motik",
title = "{Integrated Development Environment for Specifying Distributed Systems}",
school = "Faculty of Electrical Engineering and Computing, University of Zagreb, Croatia",
month = "February",
year = "1996",
type = "Diploma Thesis",
note = "In Croatian",
}