[sc34wg3] Association items

[Lars Marius Garshol]

* Nikita Ogievetsky
| 
| Not in the "instance-of" PSI, although it translates to it. For
| example:
| 
| <association>
|    <instanceOf>
|        <topicRef xlink:href="#has-quality"/>
|    </instanceOf>
|    <member>
|        <roleSpec>
|          <topicRef xlink:href="#quality"/>
|        </roleSpec>
|        <topicRef xlink:href="#inquisitive"/>
|    </member> 
|    <member>
|        <roleSpec>
|          <topicRef xlink:href="#person"/>
|        </roleSpec>
|        <topicRef xlink:href="#jan"/>
|    </member>
| </association>

Ah, yes. This is an alternative way to model the same thing;
effectively a generalization of the unary association. The usual
is-finished/is-alive examples could be translated the same way.
 
| I was running out as I typed: not sure myself what I meant :-)

Okay. :-)
 
| In any case, I think that real case for unary associations is in the
| data gathering exercise, rather then in data modeling.

What's the difference?
 
| On the other hand, here is a brief summary of my understanding of
| the confusion related to this subject:
| 
| Some people believe that there is no such thing as an "invalid topic
| map".  Like there is no such think as an "invalid opinion".

I'm not sure I agree with this. I think the situation for topic maps
is the same as for XML: If you don't meet the syntax rules it's not a
topic map (ie: invalid XTM is not a topic map, it's just an XML
document). Similarly, if the topic map is not valid by schema X, well,
then it's not valid by schema X, but it's still a topic map, and it
could still be valid by schema Y.
 
| Others believe that topic maps should compete with RDF as an
| inference-enabling technology.

I don't think that's a competition we should enter. Topic maps are, by
their very structure, optimized for a different purpose. You can still
do logical inferencing on them, but I think one could legitimately
question whether that's a primary concern for topic maps.
 
| For some people associations mean "typed" sets, and as sets they can
| be empty or unary.

TMDM (and XTM) do not accomodate this view, as associations must have
at least one role.
 
| For others associations are typed relationships and so there are
| should be 2+ related "things"/"subjects"/"players".

I think this is where Patrick started from. I guess he reacted to the
"relationship between one or more subjects", and specifically the
"one" alternative, since having a relationship between one subject
sounds kind of odd.

-- 
Lars Marius Garshol, Ontopian         <URL: http://www.ontopia.net >
GSM: +47 98 21 55 50                  <URL: http://www.garshol.priv.no >