[SCL] Proposed additions to the SCL draft standard

[Chris Menzel]

On Sun, May 25, 2003 at 11:19:35PM -0400, John Sowa wrote:
> ...
> CM> I see the need for annotations in SCL implementations, but the suggested
> >approach won't work.  You propose including them as terms.  But the
> >underlying logic/semantics of SCL is classical, and in a classical
> >semantics all terms must have a semantic value.
> 
> All terms, yes.  But the abstract syntax can specify things which
> are not terms and which do not have a semantic value.  I think that
> it would be better to adopt the principle that for every syntactic
> rule there is a corresponding semantic rule.
> 
> For an example using BNF rules, a language might have a rule that
> defines a constituent X as an A followed by a B:
> 
>    X -> A B
> 
> Then if we wanted to annotate X, we could extend that rule by saying
> 
>    X -> A B [ Comment ]
> 
> This says that X could be annotated with an optional comment
> following the constituent B.  But the semantic interpretation would
> be identical to the interpretation of the rule without the comment.

I see now that Tanel was proposing essentially this idea.  Apologies to
him for not recognizing this.  I was focused too much on the fact that
he wanted to classify them as *terms*, and that simply won't do; terms
have denotations.  But that's a quibble; there is no technical reason
why they can't be incorporated as semantically uninterpreted elements of
the syntax.

That said, I still have my concerns about adding annotations at the
level of abstract syntax.  It seems to me they should be added in
concrete SCL languages implementations.  And don't we now have to
require that some (fragment of) a natural language be incorporated into
every SCL lexicon to accommodate the formulation of annotations??
That strikes me as undesirable.

-chris