Revising Beliefs in a Multi-Source Environment

Since the seminal, philosophical and influential works of Alchourr'on, Gardenfors and Makinson, ideas on "belief revision" have been progressively refined toward normative, effective and computable paradigms. Side by side to this "symbolic" line of research, there has been also a "numerical" approach to belief revision whose main contributes were the probabilistic and the evidence-based approaches. The opinion expressed in this paper is that, to be applied in a multi-sources environment, belief revision has to depart considerably from the original framework. In particular, it has to abandon the fundamental principle of "Priority to the Incoming Information" in preference to what we called the principle of "Recoverability". Furthermore the semantic approach should be blended with a syntactic treatment of consistency inspired by the Truth Maintenance Systems