Convertibility in Databases
J.H. ter Bekke

Introduction
The relational model for databases is based on a small number of mathematical concepts. For integrity reasons (i.e. to avoid unmanageable collections of data) some other concepts have been in the database. The concept of primary key reflects a property of an individual object but also a property of an object type. Because a specific type of primary key is connected with a specific base relation, it is stated that the relation contains data about a certain type of object. Unfortunately, this concept insufficiently guarantees that every object in the database corresponds with one object in reality. Therefore, the concept of convertibility in databases is introduced. Convertibility suggests that base relations should be interpreted as collections of assertions (consisting of subject and predicate) instead of as collections of predicates (as usual in relational database theory). This concept visualizes the evaluation in data modeling from programming to databases. The concept of convertibility will be introduced with an example. This leads to new arguments for using only normalized relations (i.e. with simple attributes) in schemas of relational databases.

Publication Data
Information Processing Letters, Volume 11, number 4,5 (12 December 1980), pp. 168 - 171
Publisher: North Holland Publishing Company, Amsterdam
Year: 1980

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