Dick de Jongh

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The non-classical, nonmonotonic inference relation associated with the answer set semantics for logic programs gives rise to a relationship of strong equivalence between logical programs that can be verified in 3-valued Gödel logic, G3, the strongest non-classical intermediate propositional logic (Lifschitz, Pearce and Valverde, 2001). In this paper we will(More)
This thesis is mainly concerned with the definability issue when modal logic is interpreted on topological spaces. A topological analogon of Goldblatt-Thomason theorem is proved. Some new topological constructions are introduced. One of them, namely the notion of compact extension, is a generalization of the concept of Stone-Čech compactification known in(More)
This article is a report on research in progress into the structure of finite diagrams of intuitionistic propositional logic with the aid of automated reasoning systems for larger calculations. Afragment of a propositional logic is the set of formulae built up from a finite number of propositional variables by means of a number of connectives of the logic,(More)
This paper contains a completeness proof for the system ILW, a rather bewildering axiom system belonging to the family of interpretability logics. We have treasured this little proof for a considerable time, keeping it just for ourselves. Johan’s fiftieth birthday appears to be the right occasion to get it out of our wine cellar.