[tmql-wg] Re: [topicmapmail] AsTMa! as TMCL

[Lars Marius Garshol]

* Kal Ahmed
| 
| 1) There is nothing in the document about the treatment of
| conflicting constraints. Especially where a topic may have multiple
| types, it could be quite easy to end up with such conflicts. There
| should be some form of resolution (perhaps precendence rules based
| on file order ?)

We had this issue in OSL as well, and the language allows you to say
what other classes instances of a particular class are allowed to be
instances of. This is necessary in order to avoid having people make
statements like "Puccini is a composer and a city", which might
otherwise go through with no problem.

This is rather tricky to deal with in practice, however. We arrived at
the conclusion that if A is an instance of B and C that must mean that
it has to conform to the constraints on both. We've implemented it
that way, but in a way that is not optimal. 

The problem is that there's no guarantee that the constraints on B and
C are compatible. It's perfectly possible for the constraints to be
phrased in such a way that no instance can conform to both at the same
time. Our implementation does not detect that, but it should.
 
| 2) There are no provisions for quantitative constraints (e.g. an
| association of type 'has-natural-children' must contain no more than
| two 'parent' role-players)

OSL has this.
 
| 3) As a smaller niggle, why do regular expressions which contain a /
| character require a different syntax to other regex's when Perl
| regex's allow / to be escaped ?

OSL doesn't have this problem, because it doesn't have regular
expressions at all. :-)
 
| As an aside, it is interesting that most constraint language
| proposals involve the creation of a new syntax for their
| expression. Having started down the road of developing a constraint
| language using XTM syntax (based on the original work done by Steve
| Newcomb and Michel Biezunski on association templates), I am aware
| of the verbosity of such a solution, but it would be nice to see
| if/how a constraint language such as AsTMa! could be mapped into
| topic map constructs (even if the original AsTMa! syntax is
| retained).

Very much agreed. I've wanted to create an OSL -> topic map mapping
for a long time, but have been unable to find the time to do it. I
think this would be an important piece of work, as it would help us
find out how feasible/useable this approach would be.

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