[news.eclipse.modeling.mdt] Re: Derive constraints

["Christian W. Damus" <cdamus@xxxxxxxxxx>]

Hi, Kenn,

Right, I tend to think of derivations as constraints, too, because they're
specifications (not implementations).  :-)

I'll be interested to see what the IMM comes up with.  In my opinion, OCL is
very simple (by design) such that it hardly requires savvy-ness.  But, I do
understand the "second-class" argument, too.  Although constraints are, of
course, and integral and essential part of any model (and thus
first-class), they do take have a very different structure from built-ins
like subsetting and multiplicity.

Thanks again!

cW

Kenn Hussey wrote:

> Christian,
> 
> Some of the "additional" operations in UML are for the purposes of
> invariant constraints, but others are not. Some (a small number) of them
> are defined specifically to provide the derivation for derived properties.
> 
> Regarding the IMM specification, those of us that are OCL savvy asked the
> same question of those that were proposing an alternative (simple)
> formalism. I think it comes down to a decision about which things need to
> be "first class" concepts in the metamodel (like multiplicities,
> redefinitions, etc.) and which should get "second class" (e.g. via
> constraints) treatment...
> 
> Kenn

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