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Entity-relationship-attribute designs and sketches

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Michael Johnson, Robert Rosebrugh and R.J. Wood

Entity-Relationship-Attribute ideas are commonly used to
specify and design information systems.
They use a graphical technique for displaying the
objects of the system and relationships among them.
The design process can be enhanced by specifying
constraints of the system and the natural environment
for these is the categorical notion of sketch.
Here we argue that the finite-limit, finite-sum sketches
with a terminal node are the appropriate class and call them
EA sketches. A model for an EA sketch in a lextensive category
is a `snapshot' of a database with values in that category.
The category of models of an EA sketch is an object of models
of the sketch in a 2-category of lextensive categories.
Moreover, modelling the *same* sketch in
certain objects in other 2-categories defines both the
query language for the database and the updates (the dynamics)
for the database.

Keywords: sketch, model, database, update.

2000 MSC: 18C30, 68P15.

*Theory and Applications of Categories*, Vol. 10, 2002, No. 3, pp 94-112.

http://www.tac.mta.ca/tac/volumes/10/3/10-03.dvi

http://www.tac.mta.ca/tac/volumes/10/3/10-03.ps

http://www.tac.mta.ca/tac/volumes/10/3/10-03.pdf

ftp://ftp.tac.mta.ca/pub/tac/html/volumes/10/3/10-03.dvi

ftp://ftp.tac.mta.ca/pub/tac/html/volumes/10/3/10-03.ps

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