Supervisor

Suitable for

Abstract

Background:

The next revolution in Web search as one of the key technologies of the Web has just started with the incorporation of ideas from the Semantic Web, aiming at transforming current Web search into some form of semantic search and query answering. Next-generation technologies for semantic search and query answering on the Web can be realized via knowledge bases extracted from the Web relative to an underlying ontology. Such knowledge bases require probabilistic data models, along with scalable query answering algorithms, which are both still major unsolved problems. They may be based on integrating (i) ontology languages, (ii) database technologies, and (iii) formalisms for managing probabilistic uncertainty.

Potential Projects: 

● Characterization of ranking for non-probabilistic ontologies via explicitly defined user preferences. Key questions involve how to represent the user preferences, how to automatically obtain them (e.g., from the Web), and how to use them for ranking answers to ontological queries over knowledge bases.

● Extension of the above ranking techniques to probabilistic ontologies, i.e., combining the relevance of an answer with the probability that it is in fact true.

● Characterization of top-k query answering based on user preferences, and extension to probabilistic ontologies.

● Implementation of ranking and top-k querying on fragments of probabilistic Datalog+/-.

● Adaptation of sampling techniques for efficient query answering in probabilistic ontologies.

● Experimental evaluation of implementations over both synthetic and real-world data.

Prerequisites:

Participation in all aspects of the project require good analytical skills, and background in knowledge representation and reasoning (in particular, first-order logic and logic programming). For the theoretical aspects, background in computational complexity and database theory would be ideal. The practical (implementation-oriented) parts require software engineering skills, knowledge of Web programming to develop Web interfaces, as well as good knowledge of Java and Eclipse.

Supervision:

The projects will be supervised by Thomas Lukasiewicz.