An extended owner-coupled set data model and predicate calculus for database management
- 1 December 1978
- journal article
- Published by Association for Computing Machinery (ACM) in ACM Transactions on Database Systems
- Vol. 3 (4) , 385-416
- https://doi.org/10.1145/320289.320294
Abstract
A data model is presented, based on the extension of the concept of a DBTG owner-coupled set to permit static and dynamic sets and a new kind of set referred to as a virtual set. The notion of connection fields is introduced, and it is shown how connection fields may be used to construct derived information bearing set names, and hence permit the specification of (dynamic) sets which are not predeclared in a schema. Virtual sets are shown to reflect the functional dependencies which can exist within a file. A technique which permits the data model to be fully described diagrammatically by extended Bachman diagrams is described. A predicate calculus for manipulation of this data model is presented. Expressions written in this calculus are compared with corresponding expressions in a relational predicate calculus, DSL ALPHA. An argument for the relational completeness of the language is given.Keywords
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