Information Systems Group

― Knowledge Representation and Reasoning

Giorgos Stoilos

Research Assistant


My research interests include most aspects of knowledge representation and automated reasoning, especially focused on Description Logics (DLs) and ontology languages, such as OWL, as well as their application in areas like the Semantic Web and Multimedia. Recently I work on the topic of automatic evaluation and benchmarking of Description Logic and Semantic Web query answering systems, where I have designed and developed methods for the automatic generation of synthetic testing data and conjunctive queries. Most algorithms have been implemented in the prototype SyGENiA tool. Furthermore, I participate in the development of the HermiT reasoner where I have developed HermiT's new optimised classification algorithm. I am also currently working on query rewriting algorithms and semantic approximation.

In the past, I have also worked on the problem of representing and reasoning with fuzzy knowledge where I have developed fuzzy extensions of Description Logics and OWL, as well as a number of tableaux reasoning algorithms for them. Several of the algorithms have been implemented in the FiRE fuzzy reasoner and the ONTOSEARCH2 system. Last but not least I have also worked in the area of knowledge interoperability and ontology alignment, where I designed a new String similarity method, called Iterative-SubString (I-Sub), which has been integrated in several popular Ontology Alignment and Schema Matching Systems and recently in the NLP package of SWI-prolog.


Before coming to Oxford, I worked as a Research Assistant in the Image, Video and Multimedia Laboratory, Electrical and Computer Engineering, National and Technical University of Athens, where I also obtained my PhD under the joint supervision of Prof. Stefanos Kollias and Lecturer Giorgos Stamou. During my stay there I had the opportunity to work in a number of EU funded research projects, like the IP project X-Media, STREP project BOEMIE for which I also acted as a WP leader and NoE projects Knowledge Web and K-Space.


Outstanding paper award at the 24th AAAI Conference on Artificial Intelligence, for the paper "How Incomplete Is Your Semantic Web Reasoner?".

Best Thesis award in the National and Technical University of Athens, sponsored by the Chorafas Institute.

Recent Publications

Optimising Ontology Classification by Birte Glimm, Ian Horrocks, Boris Motik and Giorgos Stoilos. In Proceedings of the Ninth International Semantic Web Conference (ISWC 2010).

What to Ask to An Incomplete Semantic Web Reasoner? by Bernardo Cuenca Grau and Giorgos Stoilos. In Proceedings of the 22nd International Joint Conference on Artificial Intelligence (IJCAI−2011).

How Incomplete is your Semantic Web Reasoner? by Giorgos Stoilos, Bernardo Cuenca Grau and Ian Horrocks. In Proceedings of the Twenty-Fourth AAAI Conference on Artificial Intelligence (AAAI 2010). AAAI Press. 2010.


In my younger days I used to play tennis at a sub-professional level in the Juniors categories. I used to be a member of the Greek national team under the 18 and played in many European championships, where I had the opportunity to meet and play with people that are now competing in Grand Slams. In 1998 we managed to come 8th at the European Team Championship 18U/Edmond de Galea Cup. Whenever I find extra time from research I also go and play with Oxford's blues team.


Giorgos Stoilos


Research Assistant



Contact Information

Room 307, Wolfson Building, Parks Road
Oxford OX1 3QD


IQAROS Query Rewriting System

HermiT reasoner



Awards at the ORE 2013 workshop

MORe, HermiT and ELK, three OWL reasoning systems developed in the Knowledge Representation and Reasoning (KRR) group, have been awarded at the OWL Reasoner Evaluation Workshop (ORE 2013).

OWL Reasoner Evaluation Workshop (ORE 2013)

The KRR group co-organises the 2nd edition of the OWL Reasoner Evaluation Workshop (ORE), collocated with DL 2013 workshop.

Best paper prize at SWAT4LS'12

Doctoral Student Despoina Magka's paper entitled 'Ontology-Based Classification of Molecules: a Logic Programming Approach' has received the best paper prize at the 2012 Semantic Web Applications and Tools for Life Sciences workshop [more information].

Boris Motik awarded EPSRC Early Career Fellowship

Boris Motik was recently successful in gaining an EPSRC Early Career Fellowship. The 5 year project, MaSI3: A Massively Scalable Intelligent Information Infrastructure, focuses on Ontology-based Data Management Systems (ODMSs). These are a new kind of data management system specifically designed to deal with complex data, by using natural language queries often across multiple relevant sources [more information].

KRR member wins 'doctoral award' from University of Manchester

Yavor Nenov's PhD thesis "Computability of Euclidean Spatial Logics" has been awarded the Best Thesis Prize of the School of Computer Science at the University of Manchester [more information].

Ian Horrocks (KRR group leader) elected to Academia Europaea

Ian Horrocks has been elected to join Academia Europæa, an eminent organization for European scholars. Academia Europæa was founded in 1988 and has over 2000 members, including around 40 Nobel Laureates [more information].

KRR member wins 'doctoral award' from Spanish university

The Jaume I University of Castellon (Spain) has awarded a "Premio extraordinario de doctorado" (roughly translated as a Extraordinary Doctoral Award) to Ernesto Jimenez-Ruiz who is now a postdoctoral researcher at Oxford's Department of Computer Science [more information].

OAEI 2012: Matching Large Biomedical Ontologies

The KRR group organises the Large Biomedical Ontologies track within the Ontology Alignment Evaluation Initiative.