Re: self describing MOF?



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From: Jim Steel (Jim.Steel@irisa.fr)
Date: Tue 20 Apr 2004 - 13:30:50 BST


Alexander Rupsch wrote:

> 
> Hi all!
> 
> The  statement "MOF is self describing" is some kind of fuzzy to me, so 
> I need enlightenment.
> 
> The spec says: "... the MOF Model is formally defined using its own 
> metamodeling constructs."
> 
> Defining or describing to me means, explaining on thing using some other 
> things. If I have the constructs A, B, C, that means for example "A = B" 
> or "B = C + A" would be a description which contains new information. "A 
> = A" does not. That is different to be elemental.
> 
> Is it really possible to express any MOF construct with some other MOF 
> constructs without using some elemental concepts like "this is a"?

No, I don't think it is, but because MOF defines what "this is a" means, 
in terms of a relationship between an object and a class, its not a problem.

> For example "Generalizable Element" is a  generalization of "Namespace" 
> but it can't be because Namespace is not a "Generalizable Element". Yes 
> if I model that in MOF it could be, because I can use a "Class" to 
> express "Namespace" and the (in this case) meta-construct "Class" can be 
> generalized. But I'm defining MOF so can I use it? This is chicken and egg.

This is, as you suggest, a metalevel problem. Namespace is not a subtype 
of GeneralizableElement, obviously, but generalizations don't occur 
between subtypes of GeneralizableElement, they occur between instances 
of GeneralizableElement or its subtypes. So, since Namespace is an 
instance of Class (more commonly, Namespace is a Class), it can 
participate in generalizations. As you say, its very chicken and egg, 
but it stops the metalevels continuing up the tree.

> I understand that this not matter to the usability of MOF since chicken 
> and eggs are happy being (if keeping in their natural environment).
> 
> regards.

-- 
"Its only a model." - Monty Python's The Holy Grail.

Jim Steel                        Tel: +33 (0)2 99 842 554
IRISA (INRIA & Univ. Rennes 1)   Fax: +33 (0)2 99 847 171
Campus de Beaulieu               e-mail: Jim.Steel@irisa.fr
F-35042 RENNES (FRANCE)

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