[sc34wg3] SAM: Topic Identity

[sc34wg3@isotopicmaps.org]

Rereading the SAM with CXTM glasses, I notice that the Topic information
item does not require any form of identity. Each of the properties [source
locators], [subject indicators] and [subject addresses] may be empty as can
the [names] property.

It seems to me that a Topic item should have at least one locator in the
union of the [source locators] and [subject indicators] properties (this is
certainly the case for models built from XTM and HyTM and I think from LTM
too...I don't know about AsTMa). Is it really intended that one should be
allowed to create a topic map syntax that enables topics to be created with
no identity at all ? 

My feeling is that XTM and the other syntaxes have it right. A topic comes
into existence by one of the following means:

1) being declared (in which case it must have at least one Locator in the
[source locators] property)

2) being directly referenced - in which case the reference URI can be used
as a source locator

3) as a result of a subject identifier being used for a reference in a
property which is a collection of topics (e.g. subjectIndicatorRef in
scope, types, roleSpec and so on in XTM) - in which case a value for the
[subject indicators] property of the topic can be infered.

4) as a result of a subject address being used as a reference in a property
which is a collection of topics - in which case a value for the [subject
addresses] property of the topic can be infered. (Note: this is not done in
the existing syntaxes, but I see no reason why it should not be possible). 

Hence one can always infer at least one value for the union of [source
locators] [subject inidcators] and [subject addresses] properties.

Shouldn't the SAM reflect this ?

Cheers,

Kal