Re: TMQL - Proposal: Removal of reifier axis

Lars,

On 4/30/2011 5:43 AM, Lars Heuer wrote:
<snip>
> Nothing more fundamental, although there are some corner cases which
> have to be considered.
>
> If a topic reifies association A and A has an item identifier B and
> the topic has an item identifier C. What's the result for the "item
> identifier" axis? B and C? Or is it B in the context of the
> association and C in the context of the topic?
>
Good question. Don't know.

> I think the reification mechanism is somewhat underspecified in TMDM.
>
>    """
>    The act of reification is the act of making a topic represent the
>    subject of another topic map construct in the same topic map.
>    """
>
> If topic T reifies association A and T is an instance of TT. Is A an
> instance of TT?
>
Well, starting from the TMDM, we know that type/instance is *not* 
transitive:

> That is, if B is an instance of the type A, and C is an instance of 
> the type B, it does not follow that C is an instance of A. 

If you consider reification to be a form of association, then I think a 
following clause from the TMDM clears this up:

> Association items that use one or more of the subject identifiers 
> defined in this clause, but which do not conform to these structural 
> rules, are not considered to represent type-instance relationships. 

That is to say that type/instance is always declared and *only* in this 
structure.

Lacking that, reification cannot be said to mean that "A is an instance 
of TT." Lacks the proper structure.

That sounds consistent with the TMDM, at least to me.

But I think you are right about needing to clarify reification (or 
otherwise revise) in the TMDM.

Hope you are having a great weekend!

Patrick

-- 
Patrick Durusau
patrick-Q/[email protected]
Chair, V1 - US TAG to JTC 1/SC 34
Convener, JTC 1/SC 34/WG 3 (Topic Maps)
Editor, OpenDocument Format TC (OASIS), Project Editor ISO/IEC 26300
Co-Editor, ISO/IEC 13250-1, 13250-5 (Topic Maps)

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