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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1983., MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING, Bibliography: leaves 199-204., by Kuan-Tsae Huang., Ph.D.

"December 1981", Bibliography: leaf [1], "Contract ONR/N00014-77-C-0532", Kuan-Tsae Huang, Wilbur B. Davenport, Jr.

"December 1981", Bibliography: leaf [1], "Contract ONR/N00014-77-C-0532", Kuan-Tsae Huang, Wilbur B. Davenport, Jr.

Distributed database management systems (DDBMS) are amongst the most important and successful software developments in this decade. They are enabling he computing power and data to be placed within the user environment close to the point of user activities. The performance efficiency of DDBMS is deeply related to the query processing strategies involving data transmission over different nodes through the network. This thesis is to study the optimization of query processing strategies in a distributed databases environment. With the objective of minimum communication cost, we have developed a mathematical model to find a join-semijoin program for processing a given equi-join query in distributed homogeneous relational databases. Rules for estimating the size of the derived relation is proposed. The distributed query processing problem is formulated as dynamic network problem. We also extend this model to consider both communication cost and local processing cost. We extend this model to query processing in a distributed heterogeneous databases environment. A heterogeneous database communication system is proposed to integrate heterogeneous database management systems to combine and share information. The use of a database communication system for heterogeneous DBMSs makes the overall system transparent to users from an operational point of view. Problems of schema translation and query translation of the query processing in this environment are studied.

In order to bring distributed heterogeneous DBMSs which are implemented with relational, CODASYL or hierachical models together to share the information resources and build new kinds of applications, we propose to use relational model as global conceptual model and ALPHA as global nonprocedual high-level query language. We described the distributed query processing scheme in this environment. A scheme translation and query translation for CODASYL system case are discussed. Relational and Hierachical systems can be treated similarily.

We develop a mathematical model to compute the minimum communication cost of a join-semijoin program for processing a given equi-join query. Some definitions and conditions upon which this paper is based are stated. We define a query processing graph for each equ-join query and characterize the set of join-semijoin programs which solve this query. A rule for estimating the size of the derived relation is derived. The parameters for estimating the size of derived relation form a consistent parameter system. With the assumption of communication cost dominance, the cost functions are linear in the size of data transmission. An optimization problem for distributed query processing is well formulated.