[sc34wg3] TMQL: Environment Clause

[Lars Heuer]

Comments against TMQL draft dtd. 2008-07-15.

6.3 Environment Clause
======================

6.3.1 Directives
----------------

    "[...] For prefix directives each of the declared prefixes are
    manifested as topics in the environment map (6.3) by using the
    prefix identifier as topic item identifier and the namespace QIRI
    as subject identifier [...]"

There seems to be no reason why a prefix should be defined as topic.
According to ``6.3.1.`` the following would be valid::

    %prefix a http://www.example.org/
    %prefix a http://www.another-example.org/

To which subject identifier is the prefix ``a`` resolved? There is no
policy in TMQL: A user may define a prefix n times without any
conflict, but it is not defined how to resolve that prefix.

This would even get more complicated if the ``environment map``
contains a topic with the item identifier "a" or a topic with the
subject identifier "http://www.example.org/" or
"http://www.another-example.org/": The prefix declaration may enforce
a merging operation.

If TMQL would treat prefixes like CTM (c.f. draft dtd. 2008-05-15
"3.14.1 Prefix Directive"), prefixes won't cause merging operations
and TMQL would have a clear policy how duplicate prefixes are treated
(as error if a prefix is bound to different IRIs).

Best regards,
Lars
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