AN ABSTRACT RELATIONAL MODEL AND NATURAL JOIN FUNCTORS | Zendy

Akihiko Kato | Zendy

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AN ABSTRACT RELATIONAL MODEL AND NATURAL JOIN FUNCTORS

Author(s) -

Akihiko Kato

Publication year - 1983

Publication title -

bulletin of informatics and cybernetics

Language(s) - English

Resource type - Journals

eISSN - 2435-743X

pISSN - 0286-522X

DOI - 10.5109/13349

Subject(s) - join (topology) , functor , relational model , natural (archaeology) , computer science , mathematics , relational database , database , discrete mathematics , geography , combinatorics , archaeology

A meta-model for database models called an abstract relational model which is obtained by a categorical abstraction of a relational model is proposed. This meta-model represents various database models, e. g. relational, network, hierarchical models as special cases. It is proved that a natural join is the right adjoint of a decomposition in the relational model. On the other hand, in our abstract relational model a natural join is defined as the right adjoint of a decomposition. A sufficient condition is shown for a database model to have natural joins.

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