Fallback Revision with Important Multi-Subsets

Abstract-Belief revision is an interesting and important and interesting topic in artificial intelligence. AGM model is the famous methodology in belief revision. But almost all original beliefs might be changed in AGM model. In reality, there are some important beliefs in entire belief set. When belief revision, we wish belief revision operator to protect their unchangeableness as much as possible. For belief set with many important subsets (I₁ ⊆ I₂ ⊆ ... ⊆ I_n), researchers hope that the belief revision operators unchange subset I_n whenever possible, otherwise falling back on I_n-1 etc. It is namely the new belief revision, fallback revision in the paper. We also show a representation theorem for the fallback revision.