Database Abstractions: Aggregation and Generalization.

John Miles Smith, Diane C. P. Smith: Database Abstractions: Aggregation and Generalization. ACM Trans. Database Syst. 2(2): 105-133(1977)

@article{DBLP:journals/tods/SmithS77,
  author    = {John Miles Smith and
               Diane C. P. Smith},
  title     = {Database Abstractions: Aggregation and Generalization},
  journal   = {ACM Trans. Database Syst.},
  volume    = {2},
  number    = {2},
  year      = {1977},
  pages     = {105-133},
  ee        = {http://doi.acm.org/10.1145/320544.320546, db/journals/tods/SmithS77.html},
  bibsource = {DBLP, http://dblp.uni-trier.de}
}

BibTeX

Abstract

Two kinds of abstraction that are fundamentally important in database design and usage are defined. Aggregation is an abstraction which turns a relationship between objects into an aggregate object. Generalization is an abstraction which turns a class of objects into a generic object. It is suggested that all objects (individual, aggregate, generic) should be given uniform treatment in models of the real world. A new data type, called generic, is developed as a primitive for defining such models. Models defined with this primitive are structured as a set of aggregation hierarchies intersecting with a set of generalization hierarchies. Abstract objects occur at the points of intersection. This high level structure provides a discipline for the organization of relational databases. In particular this discipline allows: (i) an important class of views to be integrated and maintained; (ii) stability of data and programs under certain evolutionary changes; (iii) easier understanding of complex models and more natural query formulation; (iv) a more systematic approach to database design; (v) more optimization to be performed at lower implementation levels. The generic type is formalized by a set of invariant properties. These properties should be satisfied by all relations in a database if abstractions are to be preserved. A triggering mechanism for automatically maintaining these invariants during update operations is proposed. A simple mapping of aggregation/generalization hierarchies onto owner-coupled set structures is given.

Copyright © 1977 by the ACM, Inc., used by permission. Permission to make digital or hard copies is granted provided that copies are not made or distributed for profit or direct commercial advantage, and that copies show this notice on the first page or initial screen of a display along with the full citation.

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BibTeX

References

[1]: E. F. Codd: Further Normalization of the Data Base Relational Model. IBM Research Report, San Jose, California RJ909: (1971) BibTeX
[2]: ...
[3]: ...
[4]: John Miles Smith, Diane C. P. Smith: Database Abstractions: Aggregation. Commun. ACM 20(6): 405-413(1977) BibTeX

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