[sc34wg3] Draft Reference Model

Sam Hunting sc34wg3@isotopicmaps.org
Fri, 15 Nov 2002 13:55:04 -0500 (EST)


Thanks very much for your comments, especially those comments that
indicate you have read the whole document! (The inventories and
construction rules are about as exciting to read as, say, logarithmic
tables, but then -- since logarithmic tables enable such activities as
navigation and surveying -- this is entirely appropriate, is it not?

I will attempt to answer your questions (and also to enter them into an
issues list like that kept by Lars for the SAM. This will be useful not
only during the discussion of the RM proper, but during the discussion of
the SAM, in case it turns out that the RM has a clarifying effect on this
or that point.)

"attempt," I say, because my understanding is still a bit naive. If it
can't be written on a postcard, I just don't get it ...

> Some first comments on RM4TM
> 1. General comments on the "topic map graph".
> The definitions are much clearer than in previous version. I think it
> is now possible to propose a quite accurate rendition in a
> mathematical language that graph theory people will understand (if not
> agree with).

It's good to hear this, since I have always  felt that this was a strnegth
of the graph based approach (after all, what form of abstraction is more
powerful than math?)

However, I am not sure why it is necessary that graph people "agree" or
what they would agree on in any case. "Philosophers have only described
the world; the point is to change it." To me, the question is, does the RM
meet the requirements? (ie, the Subject Location Uniqueness

> Although it seems to me now quite clear that RM4TM is *not* likely to
> be mapped on the hypergraph model that we (P.Auillans, P.Ossona de
> Mendes, B.Vatant) have presented a few months ago, at first sight the
> hypergraph model could be mapped to some (more constrained) subclass
> of RM4TM. My concern is also to know if an axiomatization of RM4TM as
> a mathematical graph will meet a documented and well-known type of
> graph, or some weird form that nobody has cared to study yet.

I reject the word "weird." One of the first graphs that you see in a graph
theory 101 textbook will be something connected and symmetrical, like a
five pointed star. From many practical perspectives, such a graph would be
"weird" indeed. A graph like that proposed in the RM may seem "weird" to
academics because they have not considered networks of typed relationships
between subjects as an object of study. Now that, to me, is truly "wierd"
because what could be more important? So, with this work we are providing
new prospects of employment to many professors ;-)

> I will investigate on all that, and could report in Baltimore if I am giv=
en the
> opportunity to do it.

That will be great, of course. In fact, sooner than Baltimore, if you
like. Why wait?=20

> 2. Subject Identity Discriminating Properties (SIDPs) vs Other Properties=
> It is, if I get it well, the coolest thing in all the proposal, and the w=
ay to settle all
> the identity-names-scope debate.

Except that "SIDP" ishard to pronounce! (I keep saying "s-dip")

> 3. Minor various comments
> >   Well-formed node Case 3 ("a-node")
> >   The node serves as the A endpoint of two or more AC arcs.
> Why "two or more"? There are many cases of assertions with a single role =
type (take
> "sibling" for example)

Jan and Steve can jump in here and rectify any confusion I cause. However:

We felt that a relation with only one member was, by definition, not

The example I gave (when supporting your "one-armed" position) was
representing the empty set in an assertion. It seemed reasonable to me to
have an assertion typed as ap-set-setmember (ie, with an AT arc with a t-
node that had ap-set-setmember as a subject) and then one "arm" (a-c-x)
where the x node would play the set role. Since there would be no "arm"
with a role player for the "setmember" role type, voila! An empty set.
However, a c node may denote the fact that a role is "unplayed" (ie, there
is no Cx arc out to a role player, although there is a CR arc to the
role). So it seems better to model the empty set with a
"two-armed" assertion, where both roles are present, but the memebr role
is unplayed.

As to your example, in the RM there is only one player of the "sibling
role." That player, can however, be a subejct that represetns the set in
which all the siblings are members.

> Is this case ruled out by the model? I would suggest "one or more" here
> >   Well-formed node Case 4 ("c-node")
> >   The node serves as the C endpoint of a single CR arc.
> That means role type is mandatory. I'm very happy with that, vs <roleSpec=
> being optional
> in XTM 1.0.
> OTOH assertion type is still optional ...

Well, we call an assertion with no t-node "untyped." It would seem to be
that applications could make OPs from this fact, and get whatever
functionality they watned from that.

> >   Well-formed node Case 3 ("a-node")
> >   The node may or may not serve as the A endpoint of one AT=
> I'm curious about the rationale making role type mandatory and assertion =
type optional.
> (BTW both are mandatory in Mondeca ITM)

I must defer to Steve on this one.

> >   Subjects of Case 6 nodes
> > The subject of a t-node is a class of relationship,
> > including the roles that can be played in instances of the class,
> > and the values that are conferred on the properties of role players
> > by virtue of their situations as players of specific roles in instances=
 of the class.
> Those are "assertionPattern-role-rolePlayerConstraints" of the Draft Refe=
rence Model?
> Have they been put out of the graph? Or does RM4TM leaves free the way of=
 expressing those
> constraints?

In order: Yes, conceptually. The RM doesn't put them in the graph, but
it's likely that applications will ahve to as part of
bootstrapping. "Free" within the constraints of defining an application.

> >   Semantics of role playing
> >   No multiple role players of a single role type
> > Note 21:  However, the subject of a role player can be a group of subje=
cts ...
> I'm uneasy with that. Having several subjects playing the same role in an=
 assertion looks
> to me more natural than having to create first a subject which is a group=
 of subjects ...
> If I think I am linked to my children by a "father-child" relationship, h=
ave I to consider
> them first as a group? Or if I don't want that, split this assertion is s=
o many assertions
> that I have children.
> I would like the rationale of Note 21 to be expanded. On this father-chil=
d relationship,
> for example.

Here I must defer as well, but with a few comments:

1. Personally, I don't think it's harder in the implementations I've done,
   but it does take a bit of mental reversal.

2. "create first" suggests to me that you are thinking in terms of the
process by which the graph structure is created, rather than the graph
structure itself (front end vs. back end).

> Well, that's it for today I guess. More to come certainly
> Bernard
> -------------------------------------------------------------------
> Bernard Vatant
> Consultant - Mondeca
> www.mondeca.com
> Chair - OASIS TM PubSubj Technical Committee
> www.oasis-open.org/committees/tm-pubsubj/
> -------------------------------------------------------------------
> ----- Message d'origine -----
> De : "Steven R. Newcomb" <srn@coolheads.com>
> =C0 : <sc34wg3@isotopicmaps.org>
> Envoy=E9 : jeudi 14 novembre 2002 00:22
> Objet : [sc34wg3] Draft Reference Model
> > A draft of the long-awaited Reference Model is now
> > available at http://www.isotopicmaps.org/rm4tm/.
> >
> > I would like to thank:
> >
> > * Vicky Newcomb, my partner in everything, and no less
> >   so than usual in this.  She did the HTML rendition
> >   and the graphics.  (Everyone has already seen the
> >   graphics).
> >
> > * Sam Hunting and Jan Algermissen, without whose
> >   essential intellectual and spiritual contributions,
> >   and many months of constant hard work, this draft
> >   would not exist.
> >
> > * Martin Bryan, who made essential improvements to this
> >   draft.
> >
> > * Michel Biezunski, whose constant monitoring of the
> >   progress of this draft, and the insights and
> >   criticisms he contributed to the development process
> >   of the Reference Model, were invaluable.  (Also, we
> >   should all bear in mind that, without Michel's
> >   incredible and sometimes lonely persistence over many
> >   years, none of this Topic Map stuff would be
> >   happening today.)
> >
> > -- Steve
> >
> > Steven R. Newcomb, Consultant
> > srn@coolheads.com
> >
> > Coolheads Consulting
> > http://www.coolheads.com
> >
> > voice: +1 972 359 8160
> > fax:   +1 972 359 0270
> >
> > 1527 Northaven Drive
> > Allen, Texas 75002-1648 USA
> >
> > _______________________________________________
> > sc34wg3 mailing list
> > sc34wg3@isotopicmaps.org
> > http://www.isotopicmaps.org/mailman/listinfo/sc34wg3
> >
> _______________________________________________
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Sam Hunting
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