Sixth Annual IEEE Symposium on

Logic in Computer Science (LICS 1991)

Paper: Defaults and revision in structured theories (at LICS 1991)

Authors: Mark Ryan


Starting from a logic which specifies how to make deductions from a set of sentences (a flat theory), a way to generalize this to a partially ordered bag of sentences (a structured theory) is given. The partial order is used to resolve conflicts. If φ occurs below ψ, then ψ is accepted only insofar as it does not conflict with φ. The study starts with a language L, a set of interpretations M and a satisfaction relation. The key idea is to define, for each structured theory, a preorder on interpretations. Models of the structured theory are defined to be maximal interpretations in the ordering. A revision operator that takes a structured theory and a sentence and returns a structured theory is defined. The consequence relation has the properties of weak monotonicity, weak cut, and weak reflexivity with respect to this operator, but fails their strong counterparts


    author = 	 {Mark Ryan},
    title = 	 {Defaults and revision in structured theories},
    booktitle =  {Proceedings of the Sixth Annual IEEE Symp. on Logic in Computer Science, {LICS} 1991},
    year =	 1991,
    editor =	 {Giles Kahn},
    month =	 {July}, 
    pages =      {362--373},
    location =   {Amsterdam, The Netherlands}, 
    publisher =	 {IEEE Computer Society Press}