Analysis and Specification of a Universal Data Model for Distributed Data Base Systems

摘要

A Universal Data Model (UDM) was developed for distributed Data Base Management Systems (DBMS). The primary goal was to allow for the effective communication between heterogeneous, distributed DBMSs. A system requirements analysis was first performed for a Universal Data Base (UDB). Three models were selected and investigated as candidates for the UDM: the Canonical, Entity-Relationship, and Relational. Due to the complexities of the UDB, the user was restricted to writing universal queries in a Universal Data Manipulation Language (UDML) and was restricted to only one version of each of the three prominent data models in use: IMS (hierarchical), DBTG (network), and System R (relational). Criteria were established and the relational model, augemented, chosen as the UDM. Data model mapping issues were examined and included discussions on distributed information, redundant data, the support of Third Normal form, and target model specific issues. Algorithms were developed to show the mappings between the target models and the UDM. The integration of these mappings were also addressed. The syntax of a universal data definition language and data manipulation language were described.