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

Lars Marius Garshol sc34wg3@isotopicmaps.org
Mon, 23 Aug 2004 20:36:50 +0200

* Lars Marius Garshol
| I think we can identify one source of confusion here immediately.
| ISO 13250:2000 and XTM 1.0 both use the term "reify" in a different
| sense from the one it was coined for by the artificial intelligence
| community, and I think you continue to use and understand it in that
| sense.

* Steven R. Newcomb
| "Reification" is an idea and a term that is considerably older than
| AI.

I agree the term is older than AI, but the meaning in which the TMDM
uses it was coined (if you can say that in English) by the AI
community. I wasn't aware of the dictionary meaning of the term when I
wrote the previous message, and I accept your correction on that. 

So what I said about your usage of the term being "private" is wrong.

| I'm persuaded that my usage of the term is completely
| appropriate, except, perhaps, if the audience thinks the term was
| coined by or for the AI community.

Well, a technical meaning for it *was* defined by the AI community,
even if the word didn't originate there.
| I just went to Google and typed "reification".  The top-scoring web
| page (http://pespmc1.vub.ac.be/ASC/REIFICATION.htm) was a definition
| in "Principia Cybernetica Web".  I reproduce its two definitions here:
| [1] treatment of an analytic or abstract relationship as though it
|     were a concrete entity. (Young, p. l09)
| [2] The process of regarding something abstract as a material entity,
|     Whitehead's "fallacy of misplaced concreteness," e.g., the mistake
|     of confusing a system, which is a construct, with the physical
|     entity described in its terms (see general systems theory). In
|     social systems reification is encouraged by the use of language
|     and underlies many processes of constructing social
|     reality. (Krippendorff)
| I suspect your definition is similar to the one numbered [1], above.

So do I, though frankly I am not certain. When dictionaries write of
"treating an abstract entity as though it were concrete" I have no
idea what they mean.

| Perhaps we should agree to allow each other to use the terms we think
| we should use, with the proviso that each of us can always press the
| other for a deeper explanation of what we mean when we use our terms.

In private I have no problem with that, but I think it makes little
sense for different parts of ISO 13250 to use different terms for the
same thing (or the same term for different things, for that matter).

I think we should continue this discussion for a while to find out
what the consequences of that should be. (Ie: are they the same thing,
if so, which term should we prefer, etc)
* Lars Marius Garshol
| There are three problems with this usage of the term:
|   a) it confuses people who know the original meaning of the term,
* Steven R. Newcomb
| !

Let me amend that to: it confuses people who are familiar with the
computer science meaning of the term. We are, after all, operating
within computer science territory here.
* Lars Marius Garshol
|   b) it scares people, because "reify" and "reification" are
|      difficult-sounding terms, and so most people go blank whenever
|      these words are uttered, and
* Steven R. Newcomb
| Agreed.  It's unfortunate, but all my experience supports your
| remark.

It's good that we at least agree on one thing. :)
* Lars Marius Garshol
|   c) it leaves us without a term for distinguishing "reification" (in
|      the original sense of the word) from "reification" (in the ISO
|      13250:2000 sense of the word), and we do need such a term.
* Steven R. Newcomb
| I'm persuaded that 13250 uses the term in its *original* original
| sense.  13250 uses the term only once:
|        NOTE 4 The invisible heart of every topic link is the subject
|               that its author had in mind when it was created.  In
|               some sense, a topic link reifies a subject.  The
|               identity attribute of a topic link is provided to allow
|               the author of the topic link to indicate, as
|               unambiguously as possible, the subject he had in mind as
|               the organizing principle of the topic.  See the
|               definition of `subject descriptor'.

This is fine as far as it goes, but don't you think that the term
"represents" would do as well here to express the topic-subject

Also, you've now sidestepped my point c), which is that whatever we
call the topic-subject relationship we still need a term for what TMDM
calls reification.
| In Topic Maps, to reify something is to put a handle on it -- a
| handle that has material existence in the universe of human
| expressions. [...]

I'm with you on all of this, except that I would use the term
"represent" rather than "reify".
* Lars Marius Garshol
| So for all these reasons, and also because there appears to be no
| reason to change the meaning of the term when the term
| "representation" will do what we want,TMDM changes the meaning of
| the term. This has been discussed at ISO meetings, and the current
| draft uses and defines the terms carefully, but I suppose if you
| have gotten used to your own meaning of the term for many years that
| isn't necessarily enough to clear things up.
* Steven R. Newcomb
| Your words seem to accuse me of creating confusion, and of not using
| words carefully.  I regret any confusion caused, and any words
| poorly chosen.  I do try to clear up confusion, and to choose my
| words carefully.

I never meant to imply that you do not. What I was doing was really to
argue why I think the TMDM decision was the right one, and it was hard
to do that without saying negative things about the prior decision,
which I was arguing against.

| You would not be the first person to advise me to drop the word
| "reification" from my vocabulary.  It loses friends and alienates
| people.

Well, there are two more reasons, my a) and c) from the previous
posting. I realize a) has been rephrased, but I believe it still
stands as a valid reason.

| (That doesn't change the fact that, sometimes, it's exactly the
| right word, given an audience to whom the name "Whitehead" means
| something other than "a kind of skin blemish".  (;^))

Why would you say it is better than "represent"?
* Lars Marius Garshol
| where subjects in the real world are represented by abstract topics,
| which again are represented by topic items.
* Steven R. Newcomb
| OK, so do I understand correctly that the "abstract topics" are the
| *real* reifiers of the subjects -- reifiers that don't really exist
| anywhere -- and that the information items reify those abstract
| topics?

I'm not sure the "real reifiers" question is meaningful. TMDM is just
being careful to not say that the TMDM representation of topic maps is
the only possible one, and that topics have an independent existence
from the topic information item reflection of them.

Explaining things this way may be going a bit far (since it involves a
third layer that isn't strictly speaking really necessary), but it
does appear to yield text that is understandable and correct. (Feel
free to challenge me on both of those, though.)

So I would say the proxies of the subjects are the topic items in
* Lars Marius Garshol
| TMDM keeps the original definition for "subject" word for word,
| since it cannot be improved upon, and so in TMDM "subject" is
| explicitly defined as "anything whatsoever". So any item that
| represents something represents a subject, and they all represent
| something, so they all represent subjects.
* Steven R. Newcomb
| Wait, just checking.  The subjects they represent: are they the
| "abstract topics", or are they the *subjects* of the "abstract
| topics"?

The subjects of the abstract topics.
| I now gather, from your answer, that the relationship between an
| information item and a subject is embodied in a thing called a
| "topic map construct", or perhaps just called a "topic". 

Yes. However, I think you should ignore the thing in the middle; the
information item is really just a formalization of that, and we don't
really care about the difference. For practical purposes you can just
pretend that a topic and a topic item is the same thing, and so on for
topic name items and topic names, etc

| The information item reifies a subject that is a topic map construct
| (or maybe a "topic"), and that topic map construct's subject is the
| subject that is the whole reason for the existence of both the topic
| map construct and the information item.  Am I getting closer, or
| farther away?
Yep, that's it. (Again with the proviso that you can ignore the topic
map construct and just step over it.)

| What, for you, is the difference between "reify" (in the general
| philosophical sense) and "represent"?  I think it's worth talking
| about.

I don't know of any general philosophical meaning of "reify", so I
can't really answer that.
| For me, as for you, there's a big difference.  A thing can
| "represent" something without being usable as a model or expression
| of it.  For example, the Indian flag represents India, but one can't
| learn much about India from it, and there's almost no sense in which
| one can treat an Indian flag as if it were a model of India.  By
| contrast, a topic that reifies India can have, in addition to any
| information inherent in the topic, a context in a graph of topics.
| This context can be a model of India's actual relationships with
| other subjects, and it can make the topic that reifies India useful,
| in some limited way, as a model of India.  It can be treated, for
| certain limited purposes, as if it *were* India.

This is very interesting. You're arguing that if we use the dictionary
meanings of "represent" and "reify" then "reify" is more appropriate.
I'm not English, so I won't argue with that. It may or may not be

However, the *technical* meaning of "to represent" is precisely to be
able to treat something, for certain limited purposes, as if it *is*
the thing it represents. It doesn't need to constitute a model of the
thing being represented, but the purpose of the representation is
usually to be able to build such a model using the representation.

I'm beginning to wonder if the question before us is whether we want
to use technical or everyday vocabulary. I'm really surprised by this.

| The idea that, in Topic Maps, topics go beyond mere *representation*
| of their subjects, and that they in fact *reify* their subjects, is
| closely related to the idea that topic maps strive to reflect the
| fact that, in any given universe, each subject is unique.  If we
| represent a universe of subjects as a topic map, and we do it in
| such a way that each subject's reifier is the *only* reifier of its
| subject, and everything known about each subject is either inherent
| in it or connected to it, then there are very real senses in which
| each reifier is a model of the subject, within a model of a
| universe.

If I read this with my technical glasses on it sounds really bizarre.
However, now that I know what you mean by the terms it makes perfect
sense. So I really think our problem here is the choice of
terminology, rather than the meaning of the terms.
* Lars Marius Garshol
| I think you may be right here. 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.
| OK.  But why not?  

Frankly, for no particularly good reason. It's one of the infinite
number of assumptions we don't spell out. As you've now demonstrated,
this one can cause problems if not spelled out.

| It seems to me that if TMDM doesn't make ontological commitments
| about exactly how it serves as a model of actual subjects, TMDM is
| vulnerable to the (potentially devastating!)  criticism that it
| doesn't have anything to do with the representation of any subjects
| other than topic map constructs.  Why would anybody bother with a
| representation that can only represent a few kinds of extremely
| specialized subjects (the idea of a topic, the idea of an
| association, the idea of an occurrence, etc.), if they can choose a
| representation (such as RDF, for example) that can *directly*
| represent multiple broad spectra of subjects?  What advantages are
| gained by using a representation of a representation of a subject,
| as opposed to a representation of a subject?  I think it will be
| important for TMDM to articulate a compelling answer to this
| question.

Here we're not in agreement any more. The three-level model in TMDM is
just an editorial device, and you can really ignore the middle layer
and just consider two of the layers.

In any case, nobody is going to make the RDF/TM choice based on the
wording used in the standard itself. Hardly anyone is going to even
discover there is a layer in between unless we tell them.
| Exactly my worry!  An association is already a representation of a
| relationship, so an information item that represents an association
| is two removes from the relationship.  It seems to me that most
| users of Topic Maps, and of TMDM, are more interested in the
| relationship than in a representation of a relationship.  And, they
| are more interested in a representation of the relationship than in
| a representation of a representation of the relationship.

I agree fully.
* Lars Marius Garshol
| I think reification (TMDM sense!) must be taken to mean the former,
| since otherwise it is not of any use whatsoever.

* Steven R. Newcomb
| Agreed.

* Lars Marius Garshol
| (There has been quite a bit of discussion on this, but I'm not
| sure how many people have been in on it. I'll expand if anyone's
| curious.)
* Steven R. Newcomb
| I have the feeling that we're discussing it again.  Please feel free
| to expand if you have time.  Maybe we can fly over familiar
| territory, instead of slogging through it again.

I'm not sure there's any point, really, since both you and Bernard
understood what I meant, and agreed with it.
| Maybe it will turn out to be helpful, but, right now, all it does is
| to beg the questions, "What is a topic map?"  "What is a topic?",
| "What is an association?"  These questions are legitimate and
| necessary because the only formal definitions of these terms -- the
| definitions that appear in 13250 -- actually define syntactic
| constructs, but, in what follows below, you say that "topic map
| constructs" (as you use this term) are not syntactic constructs.

In TMDM these are defined as 

  3.31 topic map
  a set of topics and associations

  3.28 topic
  a symbol used within a topic map to represent some subject, about
  which the creator of the topic map wishes to make statements

  3.1 association
  a representation of a relationship between one or more subjects  

So as you say we're no longer defining them as syntactic constructs,
while ISO 13250 did so. Personally, I think defining them as syntactic
constructs is wrong, since it reflects a syntax-centric view of topic
maps, and the whole point of this model exercise was to abandon that.

| You're saying that the subject of an information item is an idea,
| and that idea is a topic map construct.  Right?

What I'm saying is that the subject of an information item is an idea,
and that the idea is the same as the subject of the topic map

| I've been trying to "play back" my understanding.  I'll appreciate
| it if you'll tell me where I seem to be going astray.

I've tried my best.
* Lars Marius Garshol
| Topic map constructs are already representations, are they not? A
| topic is a representation of a subject, right?
* Steven R. Newcomb
| Sounds both good and familiar to me.

If this is the case, why do you use "reify" instead of "represent"?
(I'm not saying there isn't a reason, just that I expect there is one,
and I don't know what it is.)
* Lars Marius Garshol
| Correct. It's outside the scope of the TMDM. XTM handles assignment
| of source locators when reading XTM files. LTM does the same for LTM
| files, and so on.
* Steven R. Newcomb
| You seem to be saying that the XTM specification will specify the
| interpretation of its instances as TMDM instances.  Is that right?

It is. The current XTM 1.1 draft does this.
| If so, will that specification implicitly or explicitly specify the
| interpretation of XTM instances as sets of topic map constructs?

Yes. (Implicitly, since it maps to TMDM, which contains a mapping to
topic map constructs.)
| What will specify how the subjects represented by the topic map
| constructs will be determined to be the same as each other?

The TMDM does this through the equality rules (which are really
subject equivalence rules).
* Lars Marius Garshol
| Well, first of all, there are no source locator items, only locator
| items. These represent URIs, or HyTime locators, or some so far
| undefined locator syntax.

* Steven R. Newcomb
| Are the locators constrained by the definitions of the interchange
| syntaxes, 

Yes, they are. XTM uses XLink, and XLink only supports URIs, so if
you are using XTM you are stuck with URIs.

| or can any sufficiently powerful locator expression be used as a
| source locator for any syntax?

It can, provided you've got a syntax that lets you put it in there.
HyTM would be one example.

(Well, in theory we could define the mapping of -id- attributes in XTM
using, say, HyTime, but since URIs work and the rest of XTM uses URIs
only, that would be a very odd decision to make.)

* Lars Marius Garshol
| The [source locators] property is used to say that the locator
| refers to the syntactic construct that the topic map construct
| represents.
* Steven R. Newcomb
| Do you really mean to say that a topic map construct represents a
| syntactic construct?  

That's a rather deep question, and one that I've had many debates on
with various people. On one level this is precisely what is happening
in the TMDM, in the sense that we've created this abstraction that
models the syntax. However, this seems to say that the syntax is
primary and that all topic map constructs represent syntactic
constructs, which is just wildly wrong. The only reason TMDM can be
said to be modelling the syntax is that that's what we started from,
by historical accident.

So, no, that's not really what I meant to say. The syntax clearly does
represent topic map constructs, but not the other way around, when
looked at in general terms.

| Until I read the above sentence, I was just getting comfortable with
| the idea that a topic map construct represents a real subject, in
| sequence of layers of representation:
|   real subject (is represented by)
|   topic map construct (is represented by)
|   TMDM information item
| Now you seem to be saying that there's an additional layer in this
| cake:
|   real subject (is represented by)
|   syntactic construct (is represented by)
|   topic map construct (is represented by)
|   TMDM information item
| Is either of the above layer cakes accurate?

I'd say the first one is. The second would also be accurate if changed
like this:

  real subject (is represented by)
  topic map construct (is represented by)
  TMDM information item (may be represented by)
  syntactic construct

Note the "may be", since there need not be any syntactic construct
that gave rise to the information item. (I'm skipping discussion of
whether "may be" is appropriate for the other layers, too.)
| You tell me.  Am I getting it, or not?

I think you are, despite me occasionally making things hard.

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