[sc34wg3] RM4TM SLUO : Objective or Requirement?

Bernard Vatant sc34wg3@isotopicmaps.org
Mon, 25 Nov 2002 14:04:23 +0100


I think your answer is clearing some points for me. Thanks for that.
A few issues remain, though. Details below.

*Bernard Vatant
> *****[1]*********
> > "In topic map graphs, only nodes can represent subjects, and every node represents a
> > single subject." [1]
> *****************
> > Question en passant : Why not use the word "topic" instead of "node"
> > throughout?

*Sam Hunting
> Steve will correct me, but in the same way we tried to reserve association
> for the SAM, and assertion for the RM, we tried to reserve topic for the
> SAM, and node for the RM. Also, graphs have nodes (unless they have
> vertices ;-)

Well, why do we need different vocabulary for RM and SAM?
It figures they do not speak about the same subjects, and in that case what are the
differences, and what is the mapping?

> > To what extent is the above different of all the existing
> > prose in ISO 13250, XTM 1.0, Published Subjects TC ... "In a topic
> > map, a topic is the formal representation of a single subject". The
>                   ^^^ if it is "the", rather than "a", then that
>                       is seeking the SLUO, is it not?

I guess my mistake comes from subtle differences in use of definite and indefinite article
in English vs French.
I certainly meant "a" , if "the" here implies unicity in English (which it would not
necessarily in French, I'm afraid ...)
"In a topic map, a topic is *a* formal representation of a single subject".

That's why I definitely prefer a mathematical expression of it ...

> > notion of having nodes in the TMG representing "implicit" subjects
> > that are not topics in the corresponding topic map is IMO extremely
> > confusing and hard to grasp.
> "Confusing and hard to grasp" is a good description of set theor[y|ies],
> at least to me -- a communication problem to be remedied with editorial
> tools. Suggestions as to sections to change?

Do you mean in the RM or in set theories? :))
Honest, I don't think it's an editorial issue. It simply means, I guess, I have not
figured out well this necessity of "implicit" topics to be explicitly represented as nodes
in the RM.

> ****[2]********
> > "In a topic map graph, every subject is represented by a single node"
> > [2]
> ***************
> See also 3.9:
>    In a well-formed topic map graph, every node represents a single
>    subject, but some subjects may be represented by more than one node. In
>    a fully merged topic map graph, every subject is represented by a
>    single node.
> In my view, only a fully-merged topic map graph would *fully* meet the
> Subject Location Uniqueness Objective.

Sure. That's a definition, right? But my point is that there is no way to recognize that
it is ever achieved ...

> NOTE: A well-formed topic map graph IS STILL EXTREMELY USEFUL.

Agreed :))

> An objective like the SLUO is just that -- a goal, an end, a telos, that
> for which we strive. In the real world of engineeering constraints,
> trade-offs must be made, but that doesn't mean that the overall objective
> is not sound.

OK. So we agree. And a fully-merged topic map graph is then a "telos", and as such cannot
be given any formal definition. OTOH, what can be formally defined is a topic map *fully
merged according to some SIDP*, which means this SIDP achieves a one-to-one correspondance
between nodes and p-values. That I am ready to buy.

> If you don't have the Subject Location Uniqueness Objective, you don't
> have a topic map, any more than the indexer would if she had two cards for
> the same entry.

Hmm. I would say you have a topic map, but a suboptimal one ...

> So, what do you mean, "only" an objective? The objective
> is the raison d'etre of the entire standard -- it needs a "shall" not a
> "should."

Hmm again. I'm not sure I would go that far, since this Objective is only a telos. What is
the way to express a Telos?
Is "We shall overcome" an Objective, or a Requirement? :))

> > But it seems that the SLUO is indeed a fundamental Requirement (in
> > other words, an Axiom of the model),
> I am not sure "axiom" is the right word. An objective is a goal, someting
> to achieve through effort. I don't think that equations can be said to
> have goals, or to achieve, since as I understand, they do not exist in
> time.

Indeed, mathematical objects are orthogonal to time. That's been widely discussed in the
literature, it's both their strength and limit.
What does the SLUO try to describe: the utopia of a process, or a conformant state of some
stage in this process? If it is an utopia, it's good as is, but forget about any formal
expression of it.
OTOH, a weaker form (achievement of SLU according to a given SIDP) can be formally

> > if I understand well various Steve Newcomb's recent comments. If it
> > is, it has to be written clearly as such, and the various other
> > requirements of the RM somehow derived from or at least proven
> > consistent with it.
> Again, I am not comfortable with the mathematical language. It is hard
> enough to prove a program consistent, let alone an international
> standard. Maybe we could use a formal specification language, like Z,
> which would have the merit of offering a "proof," but would violate
> Biezunski's principle -- "there's no point writing a standard that no one
> can understand."

The point of a consistent RM is not general public understanding, but IMO
1. to ensure that different aspects of the standard (SAM, XTM, TMCL, TMQL ...) stand on a
common consistent basis.
2. to provide support for interoperability with other standards (RDF, OWL ...)

So I am not sure Biezunski's principle applies here ;-)

> > [1] has to be taken as a pragmatic definition. A node, like a topic,
> > is intended to represent a single subject. But what this subject *is*
> > no one can really tell. This is IMO the common pragmatic approach in
> > real-world TM applications so far.
> "is" is one of those philosophical words, and Zen masters and Plato, on
> whatever plane they exist today, can argue about it....

I did not say anything else, it seems ... or did I?

> In fact, RM4TM takes a pragmatic approach -- the SIDPs are there so that
> *for the purposes of an application* what a subject "is" *can* be known.
> If we grant the use of the word "ontology", the topic map ontologies (see
> note 27) define the "is"-ness of subjects.


> > For [2] ... in controlled environments where TM have been developed,
> > the one-to-one correspondence topic-subject is assumed,
> I don't think it ought to be "assumed" -- I think it ought to be specified
> in an application definition.


> > but people are well aware of the fact that identifying the same
> > subject from distributed sources is difficult to achieve, even if
> > those sources are ontologies from the same industry.
> And?
> Another way of saying "difficult to achieve" is "opportunity for
> profit" is it not?

Well, this is an orthogonal debate ...

> Again, realize that the RM does NOT say that a topic map that does not
> fully achieve the SLUO is not useful, or not valid.
> > So [2] seems not only impossible to
> > achieve in practice, but seems to express a fundamentalist approach of
> > subjects
> Not so. ("fundamentalist," forsooth?!?) See section 4.3.2:
>     4.3.2    Subject identity is the values of SIDPs
>     All merging rules defined by a TM Application must serve the Subject
>     Location Uniqueness Objective, and all must be expressed entirely in
>     terms of the values of the SIDPs defined by that TM Application. TM
>     Applications must define sufficient SIDPs, and constrain the
>     calculations and assignments of their values, in sufficient detail to
>     support all of the merging rules defined by the TM Application.
> "... defined by a TM Application ... defined by a TM Application. TM
> Applications must define .. defined by the Application."

OK. I surrender there, and withdraw the term "fundamentalist".

> One way of looking at the RM, is as enabling the practice that will
> achieve [2] ("every subject is represented by a single node") at the
> application ("pragmatic") level.
> > ... There is *no way* to make sure that two distinct topics
> > (nodes) do not *represent in fact the same subject* because of the
> > above remark.
> In a "philosphical" sense, no -- the chasm, Plato, etc. In fact, with
> subejcts defining SIDPs, there is a way.

You mean subject identity *is defined by SIDPs*, right? In that case, we are tuned.
It goes along the line that subject identity is only arbitrary/legal/sociological and not
It is defined through an interagreement process, of which SIDP is the visible mark.

> > Subjects that are considered implicitly distinct in a
> > given topic map, on the basis that they are represented by distinct
> > topics with distinct SIDPs, might be considered identical by another
> > topic map on the basis of new discovered properties ...
> > This is a frequent process in progress of knowledge that subjects
> > considered as distinct at some point are discovered as being the same
> > later on. Think about various historical apparitions of Halley's comet
> > before Halley's discovery that they were the same one returning ...
> > So the RM has to ensure that merging does not split existing subjects,
> No, applications have to do that.


> > but it has to allow merging of subjects considered previously as
> > distinct, and admit that in many cases, the same subject will be
> > represented by different nodes, because the identity of subject for
> > those nodes has not yet been discovered ... In that spirit, SLUO
> > should be considered only as a pragmatic guideline, and not an
> > absolute Requirement.
> It's an objective. (See clause 0.2 in 8879 for a good example of what an
> objective is). It isn't an "absolute requirement." If it were, we would
> have said that well formed graphs that aren't fully merged are invalid, or
> borken, or lesser citizens, or whatever. They aren't, and we don't.
> So I hope the above discussion about the pragmatic nature of the RM
> relieves some of your concerns on these points.

It is, thanks.

> > This would lead hopefully to relax a certain number of convoluted
> > constraints discussed lately.
> As I took issue with the word "weird", and the word "fundamentalist", so I
> take issue with the word "convoluted." Words like that are a little too
> abstract for my simple mind to grasp ...

I should try to avoid them, I know, but I can't resist the temptation :)
As a matter of fact, I hate people using them either ...