[{"type":"book","title":"The semantics of rational contractions","issued":{"date-parts":[["1994"]]},"author":[{"family":"Giesl","given":"J\u00fcrgen"},{"family":"Neumann","given":"Ingrid"}],"note":"Karlsruhe 1994. (Interner Bericht. Fakult\u00e4t f\u00fcr Informatik, Universit\u00e4t Karlsruhe. 1994,29.)","abstract":"\nThis paper is concerned with the revision of beliefs in the face\nof new and possibly contradicting information. In the Logic of\nTheory Change developed by Alchourron, G\u00e4rdenfors and Makinson\nthis nonmonotonic process consists of a contraction and an\nexpansion of a set of formulas. to achieve minimal change they\nformulated widely accepted postulates that rational contractions\nhave to fulfill.\n\nContractions as defined by Alchourron, G\u00e4rdenfors and Makinson\nonly operate on deductively closed sets of Formulas. Therefore\nthey cannot be used in practical applications, eg. knowledge\nrepresentation, where only finitely representable sets can be\nhandled.\n\nWe present a semantical characterization of rational finite\ncontractions (the class of rational contractions maintaining\nfinite representability) which provides an insight into the true\nnature of these operations. This characterization shows all\npossibilities to define concrete functions possessing these\nproperties.\n\nWhen regarding concrete contractions known from literature in the\nlight of our characterization we have found that they are all\ndefined according to the same semantical strategy of minimal\nsemantical change. As this strategy does not correspond to the\ngoal of keeping as many important fotmulas as possible in the\ncontracted set, we suggest a finite contraction defined according\nto the new strategy of maximal maintenance.\n","kit-publication-id":"38694"}]