Re: Constraints and Functional Dependencies
Date: Sat, 24 Feb 2007 18:20:51 GMT
Message-ID: <7m%Dh.748$PV3.10056_at_ursa-nb00s0.nbnet.nb.ca>
Carl Federl wrote:
> <Anyone have any alternate formulas for functional dependencies or
I suggest you check out Codd's 1972 paper. The above are the algebra
operations. If one has the calculus, one does not need them, and the
> candidate keys? >
>
> My primary objection to using FOL to define constraints is that it
> would require our theory of data to have two different but similar
> languages, one for defining constraints in the FOL language and then a
> second language for manipulating relations.
>
> I will first give some definitions and then show why FOL is not
> needed.
>
> Definitions:
> Relational Manipulation Language consists of the Basic Relational
> Operators and Relational Assignment.
>
> Basic Relational Operators (BRO) are Project, Extend, Restrict,
> Product, Minus, Union and Aggregation. It is also usefull to be able
> to define and name additional relational operators derived from the
> BRO such as join and divide, but these are not mandatory.