A New Rule for Updating Evidence

Abstract. In probabilistic reasoning when we have to build a probability distribution on some events and no further information is available, we then apply the insufficient reasoning principle; i.e. we assume that the events have equal opportunities to occur. In our previous work we have observed that in the Dempster-Shafer theory of evidence the principle is not applied when using Dempster's rule of combination to combine evidence. In this paper we propose a new rule, proportional sum, for updating evidence. A comparison of this rule with Dempster's rule of combination shows that the new rule updates evidence, corresponding to the point of view of belief as generalized probability, while Dempster's rule of combination combines evidence, corresponding to the point of view of belief as evidence as indicated by Halpern and Fagin. Then we have two rules within one framework: one is for combining evidence and another is for updating evidence.