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Subject: [tm-pubsubj-comment] Recommendations for using XTM


The strawman proposal I posted on February 1st elicited a number of 
comments, but I got the feeling that it wasn't the best way for most people 
to get to grips with the issues.

Also, there is still an important question to be resolved: Whether or not 
(and if so, to what extent) we want to recommend the use of XTM.

In order to help move the discussion forward I have a new proposal. It 
takes the form of actual text to go in section 5.1 of the Recommendations 
document.

I would like to suggest that Bernard inserts it into psdoc.htm at the 
appropriate place in order to provoke a discussion. Feel free to put a 
disclaimer in there stating that it is a strawman proposal that does not 
yet have the backing of the TC (or even the author :).

It's pretty complete, but there are a few open issues left at the end.

Two PSI sets that follow these recommendations are available for online 
browsing in the Omnigator at the following URLs:

   http://www.ontopia.net/omnigator/models/topicmap_complete.jsp?tm=pubsubj.psi 

   http://www.ontopia.net/omnigator/models/topicmap_complete.jsp?tm=ontopia.psi

The source of the Ontopia PSI set is at

   http://psi.ontopia.net/ontopia/ontopia.psi

An HTML rendition is available at

   http://psi.ontopia.net/ontopia/

These are revised versions of the PSI sets originally published on 2002-02-01.

Steve


**************************** cut here *******************************

5.1 Recommendations for publishing PSI sets as topic maps
-----------------------------------------------------

This section describes recommendations for publishers who wish to use
topic maps for the purpose of publishing PSI sets. The principle
advantage of expressing PSI sets as topic maps is that the PSI sets
thereby become available in a machine processable form with clearly
defined semantics and can be used directly by topic map-aware
applications, including taking advantage of the topic map merging
facility and being accessed via a standard topic map query language.

Publishers are free to express subject indicators in any form that can
be rendered for interpretation by humans, including topic maps that do
not follow these recommendations. However, by following these
recommendations, publishers that wish to use topic maps will achieve
greater interoperability with other topic map-based PSI sets and
applications that are designed to derive the maximum potential from
them.


5.1.1 The PSI set topic map
------------------------

Each PSI set should be represented by a single topic map, called the PSI
set topic map, and each PSI set topic map should contain a single PSI
set.

The PSI set topic map should have a canonical identifier in the form of
a URL that resolves to the resource containing the topic map.

    NOTE: The examples in this section assume that the PSI set topic map
    has the following canonical location:

       http://psi.mydomain.com/my-psi-set.xtm

[ISSUE: Could xml:base be used to establish this the canonical
identifier, or should we use an occurrence on the TM topic?]

The PSI set topic map should consist primarily of topics that are
intended to be used as published subject indicators and associations
that express metadata properties of those PSIs. It may also contain
additional topics that are not intended by the publisher to be used as
published subject indicators.


5.1.2 The topic map topic
----------------------

The topic map should also contain a topic that reifies the topic map
itself. This topic, called the "topic map topic" (TM topic), is the
nexus for metadata about the PSI set and should be an instance of the
class

   http://psi.topicmaps.org/pubsubj/pubsubj.psi#psiset

   EXAMPLE:

   <?xml version="1.0" encoding="iso-8859-1"?>
   <topicMap
       xmlns="http://www.topicmaps.org/xtm/1.0/";
       xmlns:xlink="http://www.w3.org/1999/xlink";
       id="my-psi-set"
   >
     <topic id="my-psi-set-topic">
       <instanceOf>
         <subjectIndicatorRef
           xlink:href="http://psi.topicmaps.org/pubsubj/pubsubj.psi#psiset"/>
       </instanceOf>
       <subjectIdentity>
         <subjectIndicatorRef xlink:href="#my-psi-set"/>
       </subjectIdentity>
       <!-- names and occurrences -->
     </topic>
     ...
   </topicMap>

The TM topic should have at least one name and one description, and may
also have other metadata as deemed appropriate by the publisher.


5.1.3 Published subject indicator topics
-------------------------------------

Each published subject indicator in the PSI set should be a topic whose
subject is the subject that it serves to indicate. For example, the
topic whose subject is "publisher" would serve as the subject indicator
for that subject. A topic that serves as a published subject indicator
is called a PSI topic.

PSI topics should have at least one name and one description.


5.1.4 Metadata
-----------

Metadata about the PSI set and individual subject indicators should be
expressed as topic characteristics of the TM topic and the PSI topics
respectively. These recommendations define certain published subjects
for this purpose, but publishers are free to create and use additional
PSIs as required for expressing other metadata properties.

Metadata properties should be expressed using subject identity, names,
occurrences, or associations as described below. No topic should have
more than one name in a given scope or more than one occurrence of a
given type in a given scope.


5.1.4.1 Subject identity
--------------------

Subject identity should be used to indicate the published subject
indicator of a PSI topic via a subject indicator reference that
references the topic itself.

   EXAMPLE:

   <topic id="my-psi">
     <subjectIdentity>
       <subjectIndicatorRef
         xlink:href="http://psi.mydomain.com/my-psi-set.xtm#my-psi"/>
     </subjectIdentity>
     ...
   </topic>

Topics that are intended by the publisher to be used as subject
indicators may be distinguished from other topics in the topic map by
the fact that they have self-referential subject identity.

[This property corresponds to dc:identifier]

[ISSUE: What about the TM topic? Does it need an identifier? Is this the
way we establish the canonical URI of the PSI set?]


5.1.4.2 Base names
--------------

Base names should be used to indicate the title(s) of the PSI set
represented by the TM topic and the name(s) of the subjects indicated by
the PSI topics.

If no language property is specified for the PSI set, the TM topic and
PSI topics should have exactly one base name in the unconstrained scope
and may have additional base names in other scopes.

If the language property of the PSI set specifies a single language, the
TM topic and PSI topics should have either exactly one base name in the
unconstrained scope or exactly one base name in the scope of the PSI set
language, and may have additional base names in other scopes.

If the language property of the PSI set specifies multiple languages,
the PSI topics should have exactly one base name for each language, in
the scope of that language, and may have additional base names in other
scopes.

   EXAMPLE 1: No language property specified for PSI set, or name
   of subject is not language dependent: One base name in the
   unconstrained scope.

   <topic id="my-subject">
     <baseName>
       <baseNameString>My subject</baseNameString>
     </baseName>
     ...
   </topic>

   EXAMPLE 2: Subject has different names in different languages (here:
   English and Norwegian): One base name per language in the scope of
   that language.

   <topic id="my-subject">
     <baseName>
       <scope>
         <subjectIndicatorRef
           xlink:href="http://www.topicmaps.org/xtm/1.0/language.xtm#en"/>
       </scope>
       <baseNameString>My subject</baseNameString>
     </baseName>
     <baseName>
       <scope>
         <subjectIndicatorRef
           xlink:href="http://www.topicmaps.org/xtm/1.0/language.xtm#no"/>
       </scope>
       <baseNameString>Mitt tema</baseNameString>
     </baseName>
     ...
   </topic>

[This property corresponds to dc:title]


5.1.4.3 Occurrences
---------------

Occurrences should be used to express description properties of the PSI
set and the subject indicators, and may also be used to express date
properties of the PSI set, as follows:


5.1.4.3.1 Description occurrences
-----------------------------

Occurrences of type

   http://psi.topicmaps.org/pubsubj/pubsubj.psi#description

on the PSI topics should be used to provide descriptions of the subjects
indicated by the PSI topics, and may also be used on the TM topic to
provide descriptions of the PSI set. Such occurrences may be internal or
external.

If no language property is specified for the PSI set, the PSI topics
should have exactly one description occurrence in the unconstrained
scope and may have additional such occurrences in other scopes.

If the language property of the PSI set specifies a single language, the
PSI topics should have either exactly one description occurrence in the
unconstrained scope or exactly one description occurrence in the scope
of the PSI set language, and may have additional description occurrences
in other scopes.

If the language property of the PSI set specifies multiple languages,
the PSI topics should have exactly one description occurrence for each
language, in the scope of that language, and may have additional
description occurrences in other scopes.

   EXAMPLE 1: Language property of PSI set unspecified or specified
   as being a single language: One description occurrence in the
   unconstrained scope.

   <topic id="my-subject">
     ...
     <occurrence>
       <resourceData>Description of my subject.</resourceData>
     </occurrence>
   </topic>

   EXAMPLE 2: Language property of PSI set specified as being multiple
   languages (here: English and Norwegian): One description occurrence
   per language in the scope of that language.

   <topic id="my-subject">
     ...
     <occurrence>
       <instanceOf>
         <subjectIndicatorRef
           xlink:href="http://psi.topicmaps.org/pubsubj/pubsubj.psi#description"/>
       </instanceOf>
       <scope>
         <subjectIndicatorRef
           xlink:href="http://www.topicmaps.org/xtm/1.0/language.xtm#en"/>
       </scope>
       <resourceData>Description of my subject.</resourceData>
     </occurrence>
     <occurrence>
       <instanceOf>
         <subjectIndicatorRef
           xlink:href="http://psi.topicmaps.org/pubsubj/pubsubj.psi#description"/>
       </instanceOf>
       <scope>
         <subjectIndicatorRef
           xlink:href="http://www.topicmaps.org/xtm/1.0/language.xtm#no"/>
       </scope>
       <resourceData>Beskrivelse av mitt tema.</resourceData>
     </occurrence>
   </topic>

[This property corresponds to dc:description]


5.1.4.3.2 Date occurrences
----------------------

Occurrences of type

   http://psi.topicmaps.org/pubsubj/pubsubj.psi#date

on the TM topic may be used to indicate the date of the current version
of the PSI set. Scope may be used to indicate the notation used to
express the date.

   EXAMPLE:

   <topic id="my-psi-set-topic">
     ...
     <occurrence>
       <instanceOf>
         <subjectIndicatorRef
           xlink:href="http://psi.topicmaps.org/pubsubj/pubsubj.psi#date"/>
       </instanceOf>
       <resourceData>2003-03-18</resourceData>
     </occurrence>
   </topic>

[This property corresponds to dc:date]


5.1.4.4 Associations
----------------

Associations should be used to specify the language property of the PSI
set, and may be used to specify the publisher and creator properties of
the PSI set, as follows:


5.1.4.3.1 Language
--------------

Associations of type

   http://psi.topicmaps.org/pubsubj/pubsubj.xtm#languageOfPublication

between the TM topic and one or more language topics may be used to
indicate the language of the PSI set.

The TM topic should play the role

   http://psi.topicmaps.org/pubsubj/pubsubj.xtm#publication

and the language topic(s) should play the role

   http://psi.topicmaps.org/pubsubj/pubsubj.xtm#language

The implication of declaring a PSI set to be in one or more language(s)
is that the TM topic and the PSI topics either have a base name in the
unconstrained scope, or a base name in each of the languages specified,
or both; and that the TM topic and the PSI topics, to the extent that
they have description occurrences, have one description occurrence in
each of the languages specified.

   EXAMPLE: This association declares the PSI set to be in both English
   and Norwegian. (Note that two associations, one for each language,
   could have been used equivalently to the single association used
   here.)

   <association>
     <instanceOf>
       <subjectIndicatorRef
         xlink:href="http://psi.topicmaps.org/pubsubj/pubsubj.psi#languageOfPublication"/>
     </instanceOf>
     <member>
       <roleSpec>
         <subjectIndicatorRef
           xlink:href="http://psi.topicmaps.org/pubsubj/pubsubj.psi#publication"/>
       </roleSpec>
       <topicRef xlink:href="#my-psi-set-topic"/>
     </member>
     <member>
       <roleSpec>
         <subjectIndicatorRef
           xlink:href="http://psi.topicmaps.org/pubsubj/pubsubj.psi#language"/>
       </roleSpec>
       <subjectIndicatorRef
         xlink:href="http://www.topicmaps.org/xtm/1.0/language.xtm#en"/>
       <subjectIndicatorRef
         xlink:href="http://www.topicmaps.org/xtm/1.0/language.xtm#no"/>
     </member>
   </association>

[This property corresponds to dc:language]


5.1.4.3.1 Publisher
---------------

Associations of type

   http://psi.topicmaps.org/pubsubj/pubsubj.xtm#publishedBy

between the TM topic and some other topic may be used to indicate the
publisher of the PSI set.

The TM topic should play the role

   http://psi.topicmaps.org/pubsubj/pubsubj.xtm#publication

and the other topic should play the role

   http://psi.topicmaps.org/pubsubj/pubsubj.xtm#publisher

   EXAMPLE:

   <association>
     <instanceOf>
       <subjectIndicatorRef
         xlink:href="http://psi.topicmaps.org/pubsubj/pubsubj.psi#publishedBy"/>
     </instanceOf>
     <member>
       <roleSpec>
         <subjectIndicatorRef
           xlink:href="http://psi.topicmaps.org/pubsubj/pubsubj.psi#publisher"/>
       </roleSpec>
       <subjectIndicatorRef
         xlink:href="http://psi.mydomain.com/my-psi-set.xtm#myEmployer"/>
     </member>
     <member>
       <roleSpec>
         <subjectIndicatorRef
           xlink:href="http://psi.topicmaps.org/pubsubj/pubsubj.psi#publication"/>
       </roleSpec>
       <topicRef xlink:href="#my-psi-set-topic"/>
     </member>
   </association>

[This property corresponds to dc:publisher]


5.1.4.3.1 Creator
-------------

Associations of type

   http://psi.topicmaps.org/pubsubj/pubsubj.xtm#createdBy

between the TM topic and some other topic may be used to indicate the
creator of the PSI set.

The TM topic should play the role

   http://psi.topicmaps.org/pubsubj/pubsubj.xtm#publication

and the other topic should play the role

   http://psi.topicmaps.org/pubsubj/pubsubj.xtm#creator

   EXAMPLE:

   <association>
     <instanceOf>
       <subjectIndicatorRef
         xlink:href="http://psi.topicmaps.org/pubsubj/pubsubj.psi#createdBy"/>
     </instanceOf>
     <member>
       <roleSpec>
         <subjectIndicatorRef
           xlink:href="http://psi.topicmaps.org/pubsubj/pubsubj.psi#creator"/>
       </roleSpec>
       <subjectIndicatorRef
         xlink:href="http://psi.mydomain.com/my-psi-set.xtm#me"/>
     </member>
     <member>
       <roleSpec>
         <subjectIndicatorRef
           xlink:href="http://psi.topicmaps.org/pubsubj/pubsubj.psi#publication"/>
       </roleSpec>
       <topicRef xlink:href="#my-psi-set-topic"/>
     </member>
   </association>

[This property corresponds to dc:creator]


5.1.5 Human interpretable renditions
---------------------------------

Publishers who use topic maps to declare published subject indicators
may additionally make renditions of those topic maps available in some
other format (e.g., XHTML or plain text) in order to guarantee increased
interpretability for humans using applications that are not topic map
enabled.

...


5.1.6 Other issues
---------------

[TBD]

* type
* other assertions
* magic string
* URL syntax (psi as a component?)
* is the subject of a PSI topic the PS or the PSI itself?
* relationship to Dublin Core (should we use URIs like
     http://purl.org/dc/elements/1.1/publisher
   instead of
     http://psi.topicmaps.org/pubsubj/pubsubj.xtm#publisher
   where appropriate?)

[ISSUE: Is this whole self-reference thing too convoluted? An
alternative might be to use an occurrence of type "identifier" to
specify the published subject identifier. But should we then duplicate
this to establish the subject identity of the topic? If we want these
topic maps to be usefully mergeable, we have to. But again, it's messy.
Perhaps Bernard is right that we shouldn't express psi sets as topic
maps at all... If we leave the format completely open, we can always
create topic maps that have a topic for each subject in any psi set and
thereby achieve the same goal. This also removes the problem that we
feel obliged to suggest a more easily human interpretable rendition in
addition to the topic map...]

**************************** cut here *******************************


--
Steve Pepper, Chief Executive Officer <pepper@ontopia.net>
Convenor, ISO/IEC JTC1/SC34/WG3  Editor, XTM (XML Topic Maps)
Ontopia AS, Waldemar Thranes gt. 98, N-0175 Oslo, Norway.
http://www.ontopia.net/ phone: +47-23233080 GSM: +47-90827246



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