Re: self describing MOF?



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From: Shashank (shashank@icmgworld.com)
Date: Wed 21 Apr 2004 - 06:00:36 BST


The MOF Model defines a element called Constraint that can be used to attach
consistency rules to other meta-model components. A Constraint comprises:
The MOF specification does not define or mandate any particular languages for
Constraint expressions, or any particular evaluation mechanisms. Indeed, it is
legitimate for Constraints to be expressed in informal language (e.g., English)
and for validation to be implemented by ad-hoc programming. However, the
Constraints that are part of the MOF Model specification itself are expressed in
Object Constraint Language (OCL) as described in the UML specification.



Andreas Metzger wrote:

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> Dear all,
>
> is it really true that MOF contains/includes OCL?
>
> If not so, MOF might in fact not really be defined with MOF itself but
> rather its definition might rely on "external" information as Laurence
> observed in his previous mail (and which also fits nicely with my
> experience/understanding of MOF).
>
> Even if OCL was part of MOF, shouldn't there then be a definition of OCL
> ~ in the form of a MOF meta-model? This meta-model would probably rely on
> ~ structural model elements of MOF (e.g. object types, ...) that are
> defined using OCL in the first place. How should such a 'chicken and
> egg' situation be resolved without the introduction of prior/external
> knowledge of a few facts (like informally understanding what an object
> type is)?
>
> Sincerly
>
> ~  Andreas
>
> - --
> Dipl.-Inform. Andreas Metzger
> Department of Computer Science, University of Kaiserslautern, Germany
>
> Website: http://wwwagz.informatik.uni-kl.de/staff/metzger
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