Vortragsankuendigung
Hans Tompits
Institut fuer Informationssysteme,
Abt. Wissensbasierte Systeme 184/3
Default Reasoning, Blocking Sets and Block Graphs
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Thomas Linke (Universitaet Potsdam)
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Donnerstag 16.3.00, 16:00 c.t., Seminarraum 184/3, Fav.str. 11, 3. Stk.
Abstract:
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We introduce new concepts for default reasoning in the context of
query-answering in regular default logic.
For this purpose, we develop a proof-oriented approach for deciding whether
a default theory has an extension containing a given query.
The inherent problem in Reiter's default logic is that it
necessitates the inspection of all default rules for answering no matter what
query.
Also, default theories are known to lack extensions occasionally.
We address these two problems by sloting in a compilation phase before
the actual query-answering phase.
The examination of the entire set of default rules is then done only
once in the compilation phase; this allows us to inspect only the ultimately
necessary default rules during the actual query answering phase.
In fact, the latter inspection must not only account for the derivability of
the query, but moreover it must guarantee the existence of an encompassing
extension.
We address this traditionally important problem by furnishing novel criteria
guaranteeing the existence of extensions that are arguably simpler and go well
beyond existing approaches.
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