Study on reasoning rule about temporal multivalued dependency with multiple time granularities and decomposition algorithm of T4NF

This article introduces temporal multivalued dependency, a type of natural temporal constraint. In order to study the inference axiom of temporal multivalued denpendency, strong finer relation which is a natural relation among temporal types is given. A sound and complete axiomatization for TMVDs is developed. Unfortunately, unlike the case of traditional MVDs, there are usually an infinite number of TMVDs implied by a finite number of TMVDs. To overcome this problem, this paper introduce the notion of a finite closure of TMVDs, and develop sound and complete axiomatization to effectively compute finite closures. Specifically, Temporal forth normal form(T4NF) that avoids all data redundancies due to the mixed set of TFDs and TMVDs is defined. This form is proper extension of 4NF. Decomposition algorithm is presented that give lossless T4NF decomposition.