[sc34wg3] SAM-issue term-scope-def

Lars Marius Garshol sc34wg3@isotopicmaps.org
09 Jun 2002 19:45:32 +0200

In ISO 13250 the definition of scope says that scope is the union of
the themes. That is, 

  [finland = "Finland" / norwegian swedish] 

means that the name "Finland" is valid in Norwegian and that it is
also valid in Swedish.

XTM 1.0, on the other hand says that it is up to the application how
to interpret the scope.

The current SAM version[1] says scope is the intersection of the
themes, which means that this particular scope would only be valid in
*both* Norwegian *and* Swedish at the same time, which would require
the topic to be written in this way:

  [finland = "Finland" / norwegian 
           = "Finland" / swedish] 

On the other hand, that something is my opinion today could according
to the SAM be expressed by scoping it with topics representing me and
today. ISO 13250 explains in a note that to say this would require a
topic representing me today would have to be created and used as the
scope. (No mechanism is provided for doing so in ISO 13250, however.)

The question is, which of these three approaches should we choose? I
think we need to consider carefully the consequences for the
unconstrained scope, for merging, and also for querying operations.

--- Scope is union

If we say that scope is union that would mean that the following topic

  [finland = "Finland" / norwegian swedish
           = "Finland" / norwegian 
           = "Finland" / swedish] 

contains two redundancies, and is actually equivalent to

  [finland = "Finland" / norwegian swedish] 

which would seem to imply that the rules for equivalence and
redundancy elimination need to be modified.

Furthermore, if associations with published subjects are necessary to
form compound scope it means that in order to answer the question
"what occurrences of the topic 'term-scope-def' are valid in the scope
'lmg'" correctly when presented with

  {term-scope-def, opinion, ""} / lmg-today

the topic map processor would have to traverse associations to
evaluate the scope correctly, and building compound scopes becomes
very cumbersome.

--- Scope is intersection

This means that to assert that something is valid in two different
contexts requires it to be repeated. This seems like the lesser evil.
It also means that the arithmetic of scope works well with the
unconstrained scope being the empty set. (See previous email.)

--- Scope is unspecified

One of the mechanisms for merging (TNC merging) would then depend on a
feature whose meaning is unspecified.  Furthermore, when attempting to
merge topic maps that interpreted scope differently one would be bound
to get suboptimal results. Furthermore, we would have to create TMQL
scope operators for a construct whose interpretation is undefined.

In short, this does not seem to work very well.

[1] Versions of SAM prior to 1.23 had an editorial error in the
    definition of scope.

Lars Marius Garshol, Ontopian         <URL: http://www.ontopia.net >
ISO SC34/WG3, OASIS GeoLang TC        <URL: http://www.garshol.priv.no >