Anotace:
In this paper, three different frameworks for uncertainty description are considered: probability and possibility theories, and Dempster-Shafer theory of belief functions. For all of them a special operator of composition is introduced. It enables, among others, defining the concept of factorization meeting all the semigraphoid axioms. It is showed that whilst for probability and possibility theories factorization and conditional independence coincide, they differ from each other for belief functions. Since the introduced factorization manifests more of the properties required for the concept of conditional independence, the question arises whether not to substitute the used concepts by that introduced in this paper, which is based on the operator of composition.