Maintaining Sequences of Knowledge Bases in ASP
نویسندگان
چکیده
Updates of knowledge bases have become an important topic in Artificial Intelligence and a key problem in knowledge representation and reasoning. One of the latest ideas to update logic programs is choosing between models of generalised answer sets to overcome disadvantages of previous approaches. This paper is an extended proposal of a semantics for updates that performs the methods presented in previous reports of relaxing an original knowledge base and of establishing preferences amongst candidate models. In particular, the intuition behind the methodology consists in favouring the latest updates that conflict with previous knowledge bases in a sequence, by means of preferring generalised answer sets and by preserving consistency. The semantics presented in this paper satisfies a set of structural properties for sequences to update logic programs, as well as other needed properties of consistency preservation and inconsistent updates. Besides satisfying such principles, this paper illustrates, by means of several examples and transformations, how to overcome problems occurring in alternative update approaches for ASP. In particular, one of the key transformations yields an abductive program out of a given sequence of updating extended logic programs. Another transformation constructs a preferred weak-constraint program to find generalised answer sets of the abductive program. Finally, as one main goal of Logic Programming, this paper describes a functional prototype of the declarative semantics version, that finds the update answer sets of a given sequence by means of DLV’s weak-constraints models. The prototype is fully functional and runs online with a standard browser interface. The section also includes an analysis of complexity of the corresponding processes, an outline of the basic structure of the system, as well as a description of the employed technology.
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