[topicmapmail] subject indicators

[Kal Ahmed]

I think you are almost exactly right :)

If you wish to create a topic whose subject *is* an addressable resource 
(e.g. a topic about a web page), then you use the URI of the addressable 
resource as the subject identity of the topic. That is, you (in XTM) put 
the URI in a <resourceRef> element child of the <subjectIdentity> element 
of the topic.

If you wish to create a topic whose subject *is described by* an 
addressable resource (e.g. use the URL http://www.techquila.com/people/kal 
to identify the subject "Kal Ahmed"), then you would use the URI of the 
addressable resource which describes your (presumably non-addressable) 
subject as the subject indicator of the topic. In XTM, you put the URI in a 
<subjectIndicatorRef> element child of the <subjectIdentity> element of the 
topic.

Published Subject Identifiers are URIs that are used in the second manner 
described above. What makes a PSI different from a plain-old-ordinary URI 
used as a subject identifier, is that a PSI that can be resolved to a 
subject indicator - a human-readable description of the subject itself. In 
the current draft of the recommendation on PSIs [1], you can see that there 
are other recommendations regarding that resource too.

So, if you want to define a subject in an unambiguous manner and want to 
enable others to refer to that subject, then you should either seek a 
Published Subject Indicator for that subject or create one if none exists. 
Then use the address of the Published Subject Indicator as the subject 
identifier in a <subjectIndicatorRef>. You will see from the 
recommendations of the PSI commitee that Published Subject Indicators 
should be human-readable and that the emphasis is on readability in 
standard browers, and so putting your indicator *inside* the topic map 
would probably go against those recommendataion (though *repeating* your 
indicator inside the topic map might be a good thing to do).

[1] also contains a good discussion of subject identity and subject 
indicators, and the other papers produced by the PSI committee at [2] are 
definitely worth reading in this context.

Hope this helps,

Kal

[1] 
http://www.oasis-open.org/committees/tm-pubsubj/docs/recommendations/general.htm
[2] http://www.oasis-open.org/committees/tm-pubsubj/docs/index.htm


At 09:39 24/02/2003 +0100, onet wrote:
>Hello,
>
>Currently I am wiriting my master thesis titled "Topic maps". When I read
>about subject indicators I feel a little bit confused :). There are
>two kinds of subjects: addressable and non-addressable. In case of
>these first ones, subject indicators are simply URLs to the resources
>which defined these subjects as unambiguously as possible. When I want
>to assign an identity to the non-addressable subject I can use URIs (which
>contain also PSIs) or I can create my own definition inside or outside
>one of the topic maps. Am I right? :)
>
>Regards,
>Magdalena Litwin
>
>--------------r-e-k-l-a-m-a-----------------
>
>
>Tanie bilety lotnicze!
>http://samoloty.onet.pl
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