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Subject: [tm-pubsubj] Published subjects terminology



Here's my attempt to describe the terminology of published subjects.
It's still a little rough, but I hope it still helps. With feedback I
may be able to improve it.



  PUBLISHED SUBJECT TERMINOLOGY
===============================

This is a working document for the PubSubj TC, which explains the
terminology relating to published subjects from one particular point
of view. There are other points of view within the TC, so this
document is in no way official. (Thanks to Sylvia Schwab for a very
helpful outside view.)


  SUBJECTS AND THEIR PUBLISHERS
-------------------------------

(While reading it may be useful to keep an eye on this diagram:
<URL: http://www.ontopia.net/tmp/terms.png >.)

Imagine that someone wants others to be able to refer to a certain
concept in an unambiguous fashion in a global context. In topic map
terms, concepts are called /subjects/, but they have no obvious
identifiers, in topic maps or out of them. So, what to do?

One solution is to publish a /subject definition resource/ (SDR) for
the subject. This is an information resource[1] that defines clearly
(to a human reader) what the subject is. The publication of the SDR
makes the subject a /published subject/, and the interested party the
/publisher/ of that published subject.

Note that the published subject is the real-world concept we want to
make statements about, not what the publisher publishes. That is the
SDR, and its role is to explain what the published subject is. Those
who want to refer to the subject can now do so by referring to the
SDR.


  PUBLISHED SUBJECTS IN TOPIC MAPS
----------------------------------

Now, someone wants to make a topic map where they make statements
about the published subject. To do this the topic map author needs to
make a topic in the topic map and give that topic a /subject indicator
reference/ (SIR), which points to the SDR. Doing so makes the SDR a
/subject indicator/ in this topic map.

Note that any resource can be used as a subject indicator. All that's
necessary for this to happen is for someone to refer to it as a
subject indicator from some topic map. This is somewhat risky,
however, as the resource may not be completely unambiguous as to what
subject it defines, but for want of a formal SDR one may well use some
resource that seems reasonable.

Part of the reason to use published subjects is so that topic maps
will merge correctly even when written by parties unaware of one
another. When merging topic maps the topic map software will not
download and compare the subject indicators, however, and therefore
it's vital that all references to SDRs use exactly the same SIRs. For
this reason the publisher must not only publish the SDR, but also
clearly define the URI to be used to refer to the SDR.


  DOCUMENTING PUBLISHED SUBJECTS
--------------------------------

In practical terms, what this means is that the publisher needs to
publish more than just a set of SDRs. (We spoke initially of a single
subject, but subjects will rarely, if ever, be documented singly.) The
complete package of documentation published is called the /published
subjects documentation/ (PSD). This will generally contain metadata
about the publisher, the collection of published subjects and
references to each SDR. In addition, it should define the canonical
SIR to be used for each published subject, and perhaps also some
assertions about each published subject (such as names and topic
types).

There are no definite rules for what PSDs must contain, though this TC
is working to define recommendations for their contents.


  SUMMARY
---------

A published subject is a subject for which someone has published an
SDR. An SDR is an information resource published in order to clearly
define a subject for a human reader. Subjects which have no SDRs are
not published subjects. Publishers are recommended to establish sets
of published subjects by publishing a PSD package, in order to
establish the set of subjects, metadata about the set and the SIR of
each subject.

From the point of view of a topic map any information resource used to
indicate the identity of a subject is a subject indicator. The subject
indicator may be a SDR, if the subject is a published subject, or it
may not be. The URI used to refer to the subject indicator is known as
the SIR.

[1] This is what is known in RFC 2396 as a network-retrievable
    resource.


--Lars M.



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