Re: [xtm-wg] "subject-descriptor-ness" scoping topic

["Steven R. Newcomb" <srn@coolheads.com>]

[Nikita:]
> Is it true that in the proposed syntax model
> the only way to say that one topic occurs
> in another topic is by means of "association"?

It depends what you mean by "topic".  A <topic> element can be
referenced by means of <resourceRef>, like any other information
object.  Therefore, a <topic> element can be an occurrence of a
topic.  

However, if you're using <topicRef>, you're really referring to a
subject, and therefore to a topic node in the graph (since we can't
deal with subjects, really - all we can do is to regard topic nodes as
proxies for subjects).

I think you have observed something very deep, interesting, and true.
The proposed syntax model does not provide a way for a topic node (a
subject) to be an occurrence of a topic.  We are implicitly taking some
philosophical positions with this design:

* That subjects (and their proxies, topic nodes) are *not* resources,
  and therefore cannot be regarded as occurrences.

* That relationships between subjects (topic nodes) are fundamentally
  different from the relationships between subjects and their
  occurrences.  The proposed syntax model requires that relationships
  between subjects be expressed via <association>s, and relationships
  between subjects and occurrences be expressed via <occurrence>s.

> And "topicRef" always means subject descriptor of a topic?
> irrespectively of "instanceOf" and "scope" ?

I'm not sure what "irrespectively" means here, but, yes, <topicRef>s
always refer to subject descriptors, and they always demand the
existence of a topic node.  Sometimes the subject descriptor referred
to is itself a <topic>, so no additional topic node needs to be
created on account of the <topicRef>.  Sometimes the subject
descriptor is also referenced by a <topic> as its subject descriptor,
so, again, no additional topic node needs to be created.  (Remember:
no two topic nodes ever have the same subject.  Merging them is
absolutely required.)  And sometimes a topic node must be created
because there just isn't any other topic node that has the same
subject as the one that must exist because a <topicRef> was used to
identify a subject descriptor.

> In other words,
> is the following valid:
> 
> <topic>
> <baseName>smart-guy</baseName>
> <occurrences>
>    <instanceOf>publications</instanceOf>
>    <resource>
>    <scope>
>      <topicRef xlink:href="#xml"/>
>    </scope>
>    <topicRef xlink:href="urn:bla:bla:isbn:1-23234-456"
> referent="isSubject"/>
>    <topicRef xlink:href="urn:bla:bla:isbn:8-98764-987"
> referent="isSubject"/>

This doesn't make sense to me.  The name "smart-guy" leads me to
believe the subject of this topic is a person.  However, you have
pointed to an information object and said, "This information object is
itself the subject of this topic."  A person is not an information
object, so I guess I didn't understand the meaning of the name
"smart-guy".  So far, there's no real problem; I don't have to
understand the significance of a name (and I clearly don't, in this
case).

But then you do something really bizarre.  You say that a *second*
information object is also itself the subject of this topic.  So you
are apparently saying that this topic has two different subjects.  In
topic maps, it's absolutely forbidden for a topic to have more than
one subject.  So, I would have to say that this example is definitely
invalid.  (Well, no, that's not true.  It's invalid only if the two
URNs don't resolve to exactly the same information object.)

>   </resource>
> </occurrences>
> </topic>
> <topic>
> <baseName>smart-guy's-coauthor</baseName>
> <occurrences>
>    <instanceOf>publications</instanceOf>
>    <resource>
>    <scope>
>      <topicRef xlink:href="#xml"/>
>    </scope>
>    <topicRef xlink:href="urn:bla:bla:isbn:1-23234-456"
> referent="isSubject"/>

Here you're saying that this second <topic> has exactly the same
subject as the first, so, in the graph, all of the characteristics of
both <topic>s will be merged in a single topic node.  That single topic
node will have two name characteristics:

(1) "smart-guy"  and

(2) "smart-guy's-coauthor"

and two occurrences:

(1) "urn:bla:bla:isbn:1-23234-456" and

(2) "urn:bla:bla:isbn:8-98764-987"

and two subject descriptors that (probably) directly conflict with one
another:

(1) "urn:bla:bla:isbn:1-23234-456" and

(2) "urn:bla:bla:isbn:8-98764-987"


Uh, also, Nikita, your <baseName> syntax is inconsistent with the
currently-proposed DTD, so your example is invalid in that sense, too.

-Steve

--
Steven R. Newcomb, Consultant
srn@coolheads.com

voice: +1 972 359 8160
fax:   +1 972 359 0270

405 Flagler Court
Allen, Texas 75013-2821 USA

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