Equivalent Beliefs in Dynamic Doxastic Logic.
Two propositions may be regarded as doxastically equivalent if revision of an agent's
beliefs to adopt either has the same effect on the agent's belief state. We enrich the
language of dynamic doxastic logic with formulas expressing this notion of equivalence,
and provide it with a formal semantics.
A finitary proof system is then defined and shown to be sound and complete
for this semantics.