Chair for Automata Theory
of the Institute for Theoretical Computer Science,
Faculty of Computer Science at
TU Dresden
Technical Reports
2007
Franz Baader and Rafael Penaloza.
Axiom Pinpointing in General Tableaux.
LTCS-Report 07-01, Chair for Automata Theory, Institute for Theoretical
Computer Science, Dresden University of Technology, Germany, 2006.
See http://lat.inf.tu-dresden.de/research/reports.html.
Bibtex entry Abstract
Paper (PS) Paper (PDF)
Abstract
Axiom pinpointing has been introduced in description logics (DLs) to help
the user to understand the reasons why consequences hold and to
remove unwanted consequences by computing minimal (maximal) subsets of
the knowledge base that have (do not have) the consequence in question.
The pinpointing algorithms described in the DL literature are obtained as extensions
of the standard tableau-based reasoning algorithms for computing consequences from DL
knowledge bases. Although these extensions are based on similar ideas,
they are all introduced for a particular tableau-based algorithm for a
particular DL.
The purpose of this paper is to develop a general approach for
extending a tableau-based algorithm to a pinpointing algorithm. This approach
is based on a general definition of ``tableaux algorithms,'' which captures
many of the known tableau-based algorithms employed in DLs, but also
other kinds of reasoning procedures.
Franz Baader and Felix Distel.
A finite basis for the set of EL-implications holding in a finite
model.
LTCS-Report 07-02, Inst. für Theoretische Informatik, TU Dresden, Dresden,
Germany, 2007.
Bibtex
entry Abstract
Paper
(PDF)
Abstract
Formal Concept Analysis (FCA) can be used to analyze data given in the form of a formal context. In particular, FCA provides efficient algorithms for computing a minimal basis of the implications holding in the context. In this paper, we extend classical FCA by considering data that are represented by relational structures rather than formal contexts, and by replacing atomic attributes by complex formulae defined in some logic. After generalizing some of the FCA theory to this more general form of contexts, we instantiate the general framework with attributes defined in the Description Logic (DL) EL, and with relational structures over a signature of unary and binary predicates, i.e., models for EL. In this setting, an implication corresponds to a so-called general concept inclusion axiom (GCI) in EL.
The main technical result of this report is that, in EL, for any finite model there is a finite set of implications (GCIs) holding in this model from which all implications (GCIs) holding in the model follow.
Boontawee Suntisrivaraporn.
Module Extraction and Incremental Classification: A Pragmatic Approach for
EL+ Ontologies.
LTCS-Report 07-03, Chair for Automata Theory, Institute for Theoretical
Computer Science, Dresden University of Technology, Germany, 2007.
See http://lat.inf.tu-dresden.de/research/reports.html.
Bibtex entry Abstract
Paper
(PDF)
Abstract
The description logic EL+ has recently proved practically useful in the life science domain with presence of several large-scale biomedical ontologies such as SNOMED CT. To deal with ontologies of this scale, standard reasoning of classification is essential but not sufficient. The ability to extract relevant fragments from a large ontology and to incrementally classify it has become more crucial to support ontology design, maintenance and re-use. In this paper, we propose a pragmatic approach to module extraction and incremental classification for EL+ ontologies and report on empirical evaluations of our algorithms which have been implemented as an extension of the CEL reasoner.
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