On the semantics of the relational data model

ABSTRACT

The relational model for data base organization introduced clearly defined basic algebraic concepts whose properties are well understood. As a consequence, questions of a semantic nature arise. Due to the mathematical nature of the relational model, these questions cannot be answered completely by it. Therefore, a data model is discussed that takes into account basic semantic properties that object types and relationships among them apparently have in the real world. The model permits a data base to be partitioned into independent object types which are natural insertion and deletion units, and associations among them. Independent object types are described by characteristics which are meaningful modification units.This data model permits us to analyze the ideas behind the relational theory more precisely, in particular the meaning of functional dependency and normalization. Insertion-deletion rules for relations in third normal form are developed, and proposals are made to avoid some drawbacks that exist even when relations in third normal form are used as the user interface to a data base.

REFERENCES

• 1: P. A. Bernstein , J. R. Swenson , D. C. Tsichritzis, A unified approach to functional dependencies and relations, Proceedings of the 1975 ACM SIGMOD international conference on Management of data, May 14-16, 1975, San Jose, California [doi>10.1145/500080.500112]
• 2: E. F. Codd, A relational model of data for large shared data banks, Communications of the ACM, v.13 n.6, p.377-387, June 1970 [doi>10.1145/362384.362685]
• 3: E. F. Codd, "Further normalization of the data base relational model", Courant Computer Science Symposia 6, Data Base Systems, New York City, May 24-25, 1971, Prentice-Hall.
• 4: E. F. Codd, "Normalized data base structure: a brief tutorial", Proc. of 1971 ACM SIGFIDET Workshop on Data Description, Access and Control, San Diego, Nov. 1971, 1-18.
• 5: E. F. Codd, "Recent investigations in relational data base systems", Proc. of IFIP '74, North Holland Pub. Co., Amsterdam 1974, 1017-1021.
• 6: P. Cohen, J. Mylopolcus and A. Borgida, "Some aspects of the representation of knowledge", Working Paper #3, TORUS Project, Department of Computer Science, University of Toronto, submitted to IJCAI, Tbilisi, Sept. 1975.
• 7: C. J. Date and E. F. Codd, "The relational and network approaches: Comparison of the application programming interfaces", IBM Research Report RJ 1401, June 1974.
• 8: I. J. Heath, "Unacceptable file operations in a relational data base", Proc. of 1971 ACM SIGFIDET Workshop on Data Description, Access and Control, San Diego, Nov. 1971, 19-33.
• 9: H. A. Schmid and J. R. Swenson, "A basic semantic data model", to appear.
• 10: C. P. Wang and H. H. Wedekind, "Sequent synthesis in logical data base design", IBM Journal Research and Development, vol. 19, no. 1, January 1975, pp. 71-77.

INDEX TERMS

Keywords:
data base design, data structures, relational data base management systems, users view of data