[sc34wg3] More comments on the Tau model

Lars Marius Garshol sc34wg3@isotopicmaps.org
Thu, 26 Aug 2004 11:46:07 +0200

* Robert Barta
| 1) "Reificiation" exists in only ONE meaning: Making an assertion
|    a "thing to talk about".
| 2) Assume an assertion a =3D { <...>, <...>, ....<...> }. To reify it
|    it only needs a member <id, "X1234567">.
|    id (a) is then "X1234567".
|    Nothing can stop me (or you) now to use "X1234567" as a player
|    in another assertion a'.

This works, I agree. (Whether it's first class or not is a different
question. I wouldn't say so, but who cares how we describe it,
* Lars Marius Garshol
| The other problem is that it doesn't appear that members are members
| of /N/ either, which means that members cannot be reified, either.
* Robert Barta
| That's a feature, not a bug. I have no problem with others putting
| the obscenity 'reifying members' into a model, but for me this is
| clearly an abomination.

Well, the trouble is that if you are going to represent TMDM for the
purposes of querying you can't lose information. You can argue that
TMDM shouldn't let you reify association roles, of course, but the
different pieces of this standard do have to fit together.

Alternatively, you can treat association roles as assertions in \tau,
and the problem will go away. You'll get a much bulkier TMDM
representation, which may make other things harder, but it's one
possible route.
| Why? Because as you yourself say...
| [...]=20
| The fact that "a particular topic plays a particular role" is
| completely worthless by itself. What is (sometimes) interesting is
| to address "a particular topic playing a particular role in an
| assertion".

Yeah, that's my point exactly, but these two things are different in
\tau and TMDM. In \tau you can't do the latter, but in TMDM you can,
because when the value of the [reifies] property of a topic item is an
association role item you know which association item the role belongs

| But that is equivalent to addressing the assertion itself. And that
| we have.

No. Reifying a role and reifying and association is not the same, and
does not mean the same.

Let's take a parenthood association example. LMG is the child, Bj=F8rg
is the mother, and Knut is the father. The association represents the
whole fact that I was born of those two particular parents, whereas
the role my father plays represents his involvement in the event,
which is different from the event itself.
* Lars Marius Garshol
| That's one exercise I'd very much like to see the author perform. :)
* Robert Barta
| Done :-)

The exercise I was referring to was representing TMDM in \tau, and you
certainly haven't spelled out how to do that yet.

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