Improving Recovery for Belief Bases

The Recovery postulate for contraction says that any beliefs lost due to the contraction of some belief p should return if p is immediately re-asserted. Recovery holds for logically closed sets of beliefs, but it does not hold for belief bases (sets of beliefs that are not logically closed). This paper discusses the Recovery aspect of the belief base optimizing operation of reconsideration (which performs hindsight belief change) and compares it to the adherence to Recovery of traditional base and belief liberation contraction operations. We also discuss the similarities and differences between the belief base manipulations for belief liberation vs. those for reconsideration — because both approaches support the concept that removing a belief from a base might allow some previously removed beliefs to return.