Distribution Problems in Distributed Database Systems: Integration and Query Decomposition

This paper presents the solutions to some of the distribution problems in distributed databases of a bottom-up type. They are a language for integrating local relations into global relations, and an algorithm for decomposing global queries into local queries and executing inter-site joins. The language which is called GSDL is an extension of QUEL so as to express the union of relations. Our query decomposition algorithm purposes to keep directory information as small and static as possible, because their maintenance is most important from the operational viewpoint. To achieve this goal, the scheduling of transmission of local relations is decided dynamically not in an off-line fashion.