Decomposition of multiple AGM contraction: possibility and impossibility results
Sven Ove Hansson · Logic Journal of IGPL · 2014
Partial meet contraction, the standard operation of contraction in AGM theory, can straightforwardly be generalized to contractions with sets of sentences instead of single sentences as inputs (multiple contraction). The conditions under which multiple contraction can be reconstructed as the intersection of several contractions by single sentences are investigated. Although such reconstruction is possible in some special cases, the major result is that in the general case, full reconstruction is not possible. Therefore, multiple contraction adds to the expressive power of belief revision theory. It is concluded that this result highlights the importance of studying multiple belief change, and multiple conclusion logic in general.