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Re: What databases have taught me

From: erk <eric.kaun_at_gmail.com>
Date: 28 Jun 2006 12:00:49 -0700
Message-ID: <1151521249.558350.213670@b68g2000cwa.googlegroups.com>


Bob Badour wrote:
> I don't have time to read this paper right now. Recalling the last paper
> you cited referencing Alloy, I didn't see anything in it that I thought
> competed with predicate calculus. Are you suggesting it has some
> advantage for constraints over a WFF ?

Alloy uses relations as its sole data structure, with predicate WFFs to describe constraints (facts), define the effects of operations (really just a use of constraints with pre- and post- states), and to test whether certain predicates hold given the model (e.g. a target predicate for which to find a counterexample).

What I like most about Alloy is its use of relations to acquire all of the desirable properties often touted by O-O advocates: subtyping, polymorphism, etc. It doesn't depart from predicates, set theory, etc. - in fact, its treatment of atoms as singleton sets, and sets as unary relations, gives it clean syntax and typing semantics that doesn't decompose into unfettered "dynamism" as advocates of "duck typing" and such would have it.

If you saw something in Alloy that runs counter to RM (even though Alloy is not intended for data management), I'd like know, since I must have missed it.

Received on Wed Jun 28 2006 - 14:00:49 CDT

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