Re: TMQL - Proposal: Removal of reifier axis

Lars,

On 4/30/2011 6:27 AM, Lars Heuer wrote:
> Hi Patrick,
>
> [...]
>>> 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:
> I think this has nothing to do with the question if type-instance
> relationships are transitive or not, but with the question what
> "reification" implies.
>
Possibly, possibly.

I mentioned the transitive issue because my reading of the TMDM is that 
all type/instance is directly stated, that is it is never implied.

But your next point, is a reified construct interchangeable with its 
reifier? maybe a different question.

> If reification implies that A and T can be used interchangeable (since
> A has become an explicit subject represented by T), the answer if A is
> an instance of TT should be "yes". Why should reification (within a
> topic map) be treated differently from our other topic
> represents/reifies subject X mechanisms (via subject
> identifier/locator)?
>
> We accept that an IRI becomes magically a topic/subject and that we
> can make statements like
>
>      <http://psi.example.org/Bremen>  isa onto:city
>
> but if we reify something within a topic map, an extra step is needed
> and A is not an instance of TT if T reifies A and T is an instance of
> TT.
>
> Maybe I misunderstood reification, but in my understanding A should be
> an instance of TT iff T reifies A and T is an instance of TT.
>
Your understanding may be correct, but that position isn't explicit in 
the TMDM, at least not how I am reading it.

> [...]
>>> 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:
> [...]
>
> Yes, if reification is interpreted as an association and we're not
> able to reify something directly, A wouldn't be an instance of TT.
>
Hope you are having a great weekend!

Patrick

PS: About to drop off-line for a bit but will catch up when I return.


> Best regards,
> Lars

-- 
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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