[sc34wg3] TMDM doesn't specify what is reified?

Lars Marius Garshol sc34wg3@isotopicmaps.org
Mon, 23 Aug 2004 12:13:42 +0200

* Bernard Vatant
| I agree with the distinction needed between reification and
| representation, [...]

Thanks! That is useful feedback.

| >   A topic REPRESENTS its subject. The topic is an electronic symbol
| >   which stands in for, represents, the real-world thing that is the
| >   subject.
| OK - except for the "real-world" reference, as you know :))

Yep, and I agree with you there, but find a little oversimplification
useful at times. :)
| >   If the subject REPRESENTED by a topic is part of the topic map we
| >   have what the term reification was originally introduced to mean;
| >   REIFICATION is a special case of REPRESENTATION, where the thing
| >   represented is a construct in the same model that isn't a fully
| >   privileged proxy (to use TMRM terminology).
| This is slightly wrong, as detailed below. And in fact I'm not sure
| you mean what you write here, since further on you write: [...]

You are right. I didn't think of it when I wrote that paragraph, but
as you point out the full story is a bit more involved. Making this
paragraph both correct, brief, and understandable is definitely not
easy, but what I really meant was that reification is when a topic
shares its subject with a non-topic construct in the same model.
| > We say that the topic represents the topic map construct (topic
| > name, occurrence, association, whatever), but we don't say the
| > last bit, which is that the topic then represents the same thing
| > that the topic map construct represents.
| This I agree with. Indeed, the "reifying" topic does not *represent*
| the topic map construct it reifies, but the subject already
| represented by this construct. 


| And that's why we have to use a distinct verb "reify" here, and not
| "represent". If you want to "represent" the topic map construct, you
| would need another topic.

Yes again. :)
| So, I would rephrase your second paragraph above like the following :
| 	"If the subject represented by a topic is already represented
|       in the topic map by a construct that isn't a 'fully privileged
|       proxy', IOW by some representation which is not a topic, then this
|       topic is said to reify the construct.  The construct and the topic
|       which reifies it represent the same subject.  Reification just
|       brings about a simplification of the representation."

This sounds right to me.
| In short : reification is not a special case of representation, it's
| simply a relationship between two representations of the same
| subject, a complex one and a simplified one.

That's a new thought to me, but I think you are right. I guess the
best way to describe reification is as a special way to indicate what
is being represented.

It seems like the prose on reification in the TMDM will need to be
revised once this debate is over. I'll do it, but I want to wait until
we've had the debate, since there may be other eyeopeners to follow.

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