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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)
Philippa, a Greek nineteen year old student at Patras University, has just discovered that Nikos and Angela are not her true parents; she was adopted when she was six months old from an orphanage in Sao Paulo. The news really shook Philippa. Much of what she used to believe all her life about herself and her family was wrong. After recovering from the(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)
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)
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)