Minimal Models for Closed World Data Bases
نویسنده
چکیده
This paper investigates a consistent version cwaS Reiter’s closed world assumption cwa. It proves (cf. theorem 4.11) that for purely relational languages cwaS is ∀-complete with respect to minimal semantics, i.e. for every ∀-sentence φ and for every ∀-theory Σ, φ ∈ cwaS(Σ) iff Σ `min φ. Moreover, it relates cwaS to other known syntactic characterization of minimal semantics: Minker’s GCWA.
منابع مشابه
On Closed World Data Bases / 119 on Closed World Data Bases
Deductive question-answering systems generally evaluate queries under one of two possible assumptions which we in this paper refer to as the open and closed world assumptions. The open world assumption corresponds to the usual first order approach to query evaluation: Given a data base DB and a query Q, the only answers to Q are those which obtain from proofs of Q given DB as hypotheses. Under ...
متن کاملEfficient Paraconsistent Reasoning with Rules and Ontologies for the Semantic Web
Ontologies formalized by means of Description Logics (DLs) and rules in the form of Logic Programs (LPs) are two prominent formalisms in the field of Knowledge Representation and Reasoning. While DLs adhere to the Open World Assumption and are suited for taxonomic reasoning, LPs implement reasoning under the Closed World Assumption, so that default knowledge can be expressed. However, for many ...
متن کاملTowards Tractable Local Closed World Reasoning for the Semantic Web
Recently, the logics of minimal knowledge and negation as failure MKNF [12] was used to introduce hybrid MKNF knowledge bases [14], a powerful formalism for combining open and closed world reasoning for the Semantic Web. We present an extension based on a new three-valued framework including an alternating fixpoint, the well-founded MKNF model. This approach, the well-founded MKNF semantics, de...
متن کاملNon-Monotonic Reasoning Based on Minimal Models and its Efficient Implementation
A common approach to non{monotonic reasoning is to choose a set S of models (e.g. minimal, perfect or stable models) for a logic program P. Then, the meaning of P is deened as the set of all formulas which are implied logically by all models in S. For a disjunctive logic program P, we consider the set S = MMP of minimal models and get the non{montonic consequences NMP of ground disjunctions ove...
متن کاملOn Computing the Gcwa
The computational complexity of a number of problems relating to minimal models of deductive databases is considered. In particular, it is shown that Minker's gener-alised closed world assumption (GCWA) is P P 1-complete for stratiied propositional databases and P P 2-complete for non-stratiied databases. The structure of minimal models is also examined using the notion of a weak deduction tree...
متن کامل