Invited Speakers

• Bernhard Ganter, Dresden, Germany
  
  Mathematical theory makes Formal Concept Analysis versatile
  SLIDES
  
  Formal Concept Analysis, a mathematical theory based on a formalization of concept and conceptual hierarchy, has several touch points with Description Logics. Franz Baader and his group have utilized FCA results for DL purposes, and conversely there were attempts to link FCA with DL to obtain better expressivity and to gain access to DL's algorithmic machinery. A promising aspect of FCA is that it is built on the mathematical theory of ordered sets and complete lattices and that it can inherit the elaborate structure theory of these fields. Another virtue is that its communicative aspects have thoroughly been discussed. FCA has the potential to encode different approaches to data analysis and to and formalized knowledge in a unifying way. We give some examples, including conceptual scaling, background knowledge, and the recent encounter of FCA with the theory of Rough Sets.
  
  
• Georg Gottlob, Oxford, UK
  
  Taming the Infinite Chase: Query Answering under Expressive Relational Constraints
  
  An important task in Knowledge Representation is answering queries posed over a knowledge base, represented as a set of facts plus a set of rules. In this talk we address the problem of answering conjunctive queries over knowledge bases where rules are an extension of logic programming rules, that may have existentially quantified variables or the equality predicate in the head; this kind of rules are traditionally called tuple-generating dependencies (TGDs) and equality-generating dependencies (EGDs), respectively, in the database literature, but they are broadly used in Description Logics and in ontological reasoning. In this setting, the chase is an important tool for query answering; so far, most of the research has concentrated on cases where the chase terminates. We define and study large classes of TGDs under which the query evaluation problems remain decidable even in case the chase does not terminate; we provide tight complexity bounds for such cases. We also give a semantic characterisation of a class of EGDs that can be added to TGDs without interacting with them. Our results immediately extend to query containment. This is a joint work with Andrea Cali and Michael Kifer.
  
  
• Maarten Marx, Amsterdam, Netherlands
  
  XPath: (P)DL on trees.
  SLIDES
  
  The talk surveys the close connection between the XML query language XPath and description and modal logic. If we are willing to view XPath as a DL it is arguably the best known and most applied DL to date. We discuss translations between the formalisms, transferred results and use cases. XPath is developed as a query language but it can also be used for knowledge engineering, reasoning about and specifying constraints on models. In the talk we will focus on this use of XPath.
  
  
• Kent Spackman, Oregon, USA
  
  Using DL to support a very large healthcare terminology: successes and challenges
  SLIDES
  
  Developers of the Systematized Nomenclature of Medicine (SNOMED) began using DL more than ten years ago to define the meanings of codes and to support the querying of medical databases. Notable characteristics of SNOMED are its size (more than 300,000 codes), scope (all of health-related terminology) and international support. Now maintained by the International Health Terminology Standards Development Organisation (IHTSDO), a Danish not-for-profit association, the terminology has been adopted for use in at least nine countries for encoding clinical information in electronic health records. This talk will focus on the use of DL in the development of the terminology, including a summary of areas where the application of DL has worked well, and areas where we face challenges. The latter include making the terminology editing process accessible to ordinary clinical experts, and integrating the terminology into the information models used in medical records software.