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One of the crucial tasks to be performed towards the realization of the vision of the Semantic Web is the encoding of human knowledge in special structures (ontologies), using formal representation languages. Simply creating an ontology is not enough though; knowledge needs to be updated as well. There are several reasons why knowledge in an ontology would(More)
This paper investigates belief revision where the underlying logic is that governing Horn clauses. It proves to be the case that classical (AGM) belief revision doesn't immediately generalise to the Horn case. In particular, a standard construction based on a total preorder over possible worlds may violate the accepted (AGM) postulates. Conversely, Horn(More)
In the past few years, several approaches for revision (and update) of logic programs have been studied. None of these however matched the generality and elegance of the original AGM approach to revision in classical logic. One particular obstacle is the underlying nonmonotonicity of the semantics of logic programs. Recently however, specific revision(More)
Possible-world semantics are provided for Parikh's relevance-sensitive model for belief revision. Having Grove's system-of-spheres construction as a base, we consider additional constraints on measuring distance between possible worlds, and we prove that, in the presence of the AGM postulates, these constraints characterize precisely Parikh's axiom (P).(More)
We present a logical framework for modeling and reasoning about requirements evolution in the construction of information systems. We illustrate how a suuciently rich meta-level logic can formally and accurately capture intuitive ways of handling incompleteness and inconsistency in requirements and how operators that map between theories of this meta-level(More)
This paper presents a methodology for estimating users' opinion of the quality of a software product. Users' opinion changes with time as they progressively become more acquainted with the software product. In this paper, we study the dynamics of users' opinion and offer a method for assessing users' final perception, based on measurements in the early(More)