xml-dev - Re: "RDF + Topic Maps" = The Future

[Nikita Ogievetsky <nogievet@cogx.com>]

Hello Martin,

You wrote:
> I wrote
>
> > > Both RDF and Topic Maps have the same weakness: They are only as good
as
> > the
> > > semantics they are based on. Neither provides a standardized mechanism
> for
> > > recording the meaning of the characteristic
>
> You responded
>
> > I tend to disagree.
> > XTM distinguishes 2 types of topic subjects:
> > addressable and non-addressable.
> > If resource is referenced as an addressable subject, it means
> > that the subject of the topic is the resource itself
> > (just as you said, no meanings or implications)
> > Syntactically it is expressed by means or <resourceRef> element.
>
> Please do not conflate Address Identity with Subject Identity and/or
> Meaning.

Sorry, did I said "meaning"? (where?) There is no meaning here whatsoever.
it is just a pointer to a resource, just like in RDF.

>
> > Extract from [1]:
> > A subject which is an addressable information resource, considered as a
> > subject in and of itself, and not considered in terms of what the topic
> map
> > author intends it to signify.
>
> What both RDF and Topic Maps (and XML Namespaces) do is to declare that
> things that have the same address are identical.

Identical subjects yes. But topic characteristics are still distinguishable
by means of scopes!
Do not underestimate scopes!

> While historically this is
> probably not true, as different things can reside at the same address at
> different periods, this limited view of identity is sufficient for the
> short-term needs of short-lived resources.

You can use URN and add historical axes to your locator, just like NewsML
does.
So this is not a problem.
Also, if you forgot to add time range to your identifier,
you are still safer in XTM because everything that you are saying
has the scope of author's opinion attached.

> > However,
> > a resource or a set of resources can be used to identify a
non-addressable
> > subject.
> > For example I can address archives of this list to identify xml
developers
> > community.
>
> But this does not help Subject Identity. Suppose you point to my name on
the
> XML Dev list and the name Martin Bryan on the British Library Resource
> mailing list. From the addresses alone you cannot determine whether or not
> the two people sharing the same name are identical or not.

Seams that only magician could have guessed this:-))
If machine does not have enough information it can not and should not do any
inferences.
However, if I did not know you,
for me your postings on XML Dev list and your identity of being
a co-editor of ISO Topic Maps identify two different "virtual" persons:-))

As you know XTM provide several mechanisms to help merging topics:
For example, if we could narrow down due to the fact that the two above
mentioned
"Martin Bryans" have their names mentioned in the scopes of
XML, SGML, Topic Maps, knowledge  technologies and Great Britain,
a good XTM software could suggested to a HUMAN(!) operator that
this two virtual people might be one and the same person!

> > Or I can identify a book by its ISBN number (which is a record somewhere
> in
> > Bowker Data Collection Center).
> > Syntactically it is expressed by means or <subjectIdentityRef> element.
>
> What if you point to the author of ISBN  0 210 40394 3? Is there or is
there
> not any Subject Identity? (The fact that all three are identical in the
> example given can only be determined by looking for matching patterns
within
> the addressed resources, such as the use of mtbryan@sgml.u-net.com as the
> email address for all three.)

Actually if you set mtbryan@sgml.u-net.com to be a base name in the scope of
"e-mail"
or use it for URN in subjectIdentity ... the merge would have happened
automatically:-)
(and I was just calling for a magician! :-))

>
> > Extract from [1]:
> > An information resource, considered in terms of what the topic map
author
> > intends it to signify, and not considered as a subject in and of itself.
>
> That is exactly my point. Users of the topic map are dependent on the
> meaning assigned by the topic map author, without having that meaning
> recorded for later reviewers to understand/verify. The same is true of
RDF.
> The meaning is solely in the view of the metadata author.
>

But as far as I know (I might be wrong, please correct me if this is the
case)
RDF has no STANDARD! way to carry forward the origin of opinion.

> Actual meaning is much harder to determine. It is entirely dependent on
> context, both of the cataloguer and the user of the metadata. For example,
> consider the problem of indexing a picture entitled "George Bush Running
in
> Texas". You might like to consider using terms taken from one the
following
> ontology fragments:
>
> Computer --> Program --> Running
> Sport --> Athletics --> Running
> Government --> Elections -->Running
> Printing --> Ink -- Running
>
> Which should you associated with the picture? Without knowing something
> about the context of the picture you cannot determine which one to use,
> though the first and last would appear unlikely to apply. But which of the
> other two would apply.? In practice neither of them is likely to be true.
> Bush is not "running the elections" - though he may be "running in the
> elections". He is also not known for running in athletics races, though he
> is known for jogging around. Unless we know the meaning of the term being
> used in each situation we cannot accurately determine whether or not the
> term can be applied to the resource.
>
> If we just have the address, without a formal definition of the meaning
> assigned to that address, then we cannot resolve ambiguities unless we
have
> access to the address, and that contains a sufficient meaning. Neither can
> we determine whether or not the person assigning characteristics to the
> resource made a correct decision back whenever this took place, or whther
> the same characteristic is relevant in today's environment.
>
> If we have access to the subject definitions, and compare them, then we
can
> determine their equivalence, but even this is not enough. Until we know
the
> context in which the resource occurred we cannot determine which ontology
to
> apply, or which meaning to assign to a term.
>
> What is needed is a standard way of identifying the contexts in which
> resources have been created. This is where RDF could help, if it could be
> used alongside standardized classification schemes. Rather than being a
> general purpose tool that can represent any relational database, it needs,
> if the semantic web is to be a usable thing, to become a set of specific
> classification databases with recorded meanings that can be referenced by
> those seeking to associate meaning with resources.  Until this happens the
> web will never be a knowledge-base.
>
> Names and/or addresses are not enough to promote understanding.

I agree, RDF Schemas can be of really great help here!
And I also agree that there is still a long - long way to go:-((

Thanks,

Nikita.

-------------------------------------------------------
Nikita Ogievetsky, Cogitech Inc.
http://www.cogx.com
nogievet@cogx.com
(917)406-8734
Consultant in XML/XSLT/Xlink/TopicMaps
Cogito Ergo XML