 By non-prioritized belief change is meant a process in which new information is received, and weighed against old information, with no special priority assigned to the new information due to its novelty. A (modified) revision operation that operates in this way is called a semi-revision. Semi-revision of \(K\) by a sentence \(p\) can be denoted \(K?p\). A sentence \(p\) that contradicts previous beliefs is accepted only if it has more epistemic value than the original beliefs that contradict it. In that case, enough of the previous sentences are deleted to make the resulting set consistent. Otherwise, the input is itself rejected.