Re: What is a pragma?

> I suppose one question that arises is whether including such a pragma
> makes a grammar non-conforming.

I think not.

> That reticence allows them to avoid all sort of theological tangles when
> it comes to conformance judgements.

I’m willing to be fairly relaxed about what impact pragmas have on
conformance, actually. Implemenations will do what customers ask (or
pay) their implementors to make them do.

I feel like ixml is considerably simpler and more declarative than
XQuery, so we ought to be able to say something about the intent. But
if we can’t do that without working out how many angels are actually on
a particular pin, I’m going to want to live with the sorts of
generalizations that avoid those tangles.


> One snag in the rule suggested: if a pragma should not change the set of
> sentences recognized by a grammar, then doesn't a pragma meaning "reject
> input of length greater than n characters" fall on the wrong side of the
> line?  Unless the grammar would in any case reject all such sentences,
> in which case why the pragma?

Maybe that’s a pragma that introduces non-conformant behavior. We can’t
*prevent* pragmas from doing that.

> I think it might be cleaner and simpler to say that the standard
> semantics of the grammar is as defined in the spec, that the semantics
> of a pragma are implementation-defined, and that the presence or absence
> of pragmas has, by definition, no effect on the standard semantics of
> the grammar.

Fine by me.

> If people want to add that implementations SHOULD refrain from defining
> pragmas which change the set of input sentences accepted by a grammar, I
> think I would urge them to think again, but I don't currently think I
> would lie down in the road over it.  A MUST would bother me more,
> though, because it makes what looks like a potentially very tricky
> question into a conformance criterion.

A MUST would be pointless since implementors will ignore it.

Perhaps the most effective thing that could be said is: if you are
relying on the interpretation of pragmas that change the semantics of
ixml grammars in some way, you are inviting misunderstanding and
interoperability issues and on your head be it.

                                        Be seeing you,
                                          norm

--
Norm Tovey-Walsh
Saxonica