\input zb-basic
\input zb-ioport
\iteman{io-port 05350209}
\itemau{Ferm\'e, Eduardo; Krevneris, Mart{\'\i}n; Reis, Maur{\'\i}cio}
\itemti{An axiomatic characterization of ensconcement-based contraction.}
\itemso{J. Log. Comput. 18, No. 5, 739-753 (2008).}
\itemab
The authors first discuss the benefits of belief bases -- sets of logical formulas -- over belief sets -- sets of logical formulas closed under some underlying notion of logical consequence. They remind us of the definition of well-known notions of belief base contraction (functions that map a belief base $A$ and a formula $\alpha$ to a subset of $A$ that fails to imply $\alpha$ unless $\alpha$ is a tautology), namely, partial meet contraction, kernel contraction and particular cases of kernel contraction, and of their axiomatic characterizations. Then they remind us of yet another notion of belief base contraction, namely, ensconcement-based contraction, first introduced by Marie-Anne Williams in 1992, before stating a result which is the main contribution of this paper, that is, the axiomatic characterization of ensconcement-based contraction in terms of six postulates: success, inclusion, vacuity, extensionality, disjunctive elimination, and conjunctive factoring. Finally, the authors define their own new notion of belief base contraction, namely, basic AGM-related base contraction, and provide a map that shows all the relationships between all those notions of belief base contraction.
\itemrv{\'Eric Martin (Sydney)}
\itemcc{}
\itemut{logic of theory change; belief bases; base contraction; ensconcement}
\itemli{doi:10.1093/logcom/exm093}
\end