Dempster’s Rule as Seen by Little Coloured Balls

Dempster’s Rule is commonly described as an operator for fusing beliefs. While there are different possible interpretations of belief fusion, there is considerable confusion regarding the exact type of belief fusion that Dempster’s rule performs. Many alternative operators for belief fusion have been proposed, where some are based on the same fundamental principle as Dempster’s rule, and others have a totally different basis, such as the Bayesian cumulative operator. In this article we take a closer look at Dempster’s rule in order to determine exactly what type of belief fusion it performs. Our conclusion is that Dempster’s rule in fact represents a method for serial combination of probabilistic constraints, which is not suitable for fusing different beliefs on the same frame of discernment. We conclude that the non-normalised version of Dempster’s rule represents a method for multiplying orthogonal beliefs on product frames of discernment.