Interaction-Free Multivalued Dependency Sets

Multivalued dependencies (MVD) and join dependencies were introduced to study database design problems. Join dependencies can be divided into cyclic and acyclic join dependencies. A fundamental result in dependency theory is that a join Dependency is acyclic if and only if it is equivalent to a set of MVDs. In addition to this characterization it has been shown that such a set of MVDs has a cover which is a conjlict-free MVD set. Although this result gives considerable insight into the “syntactic” structure of a set of MVDs equivalent to an acyclic join dependency, the definition of a conflict-free MVD set is complex and does not provide insight into what is meant by the “semantic” notion of a set of MVDs free of conflicts. We introduce the concept of an interaction-free MVD set. In contrast to the definition of a conflict-free MVD set, the definition of an interaction-free MVD set clearly indicates that we are dealing with a’set of MVDs which do not interact in an adverse way. Furthermore, we provide a simple syntactic characterization of an interactian-free MVD set and show that a join dependency is acyclic if and only if it is equivalent to an interaction-free MVD set.