[SCL] Obvious SCL spec ideas for extensions

[pat hayes]

>Hi Chris,
>
>Wanted to point out that:
>
>Although I have proposed to have a separate
>ECL language in the SCL document, we could
>alternatively proceed by putting seqvars and the
>two kinds of predicates into the SCL modules,
>as we originally thought.

I really do not want us to have two languages. This is just 
re-inventing CL. Let us try to find a single language and keep it as 
simple as we can.

>
>This would be possible only if you manage to
>come up with a really easily understandable MT
>and abstract syntax for these two things, building
>directly on SCL core.
>
>I have no intuition if that can be done (initially
>suspected that it cannot, hence suggested a separate
>ECL language).

It it cannot, then let us discuss how to simplify the language so as 
to make it possible, rather than suggesting multiple languages.

>
>Simpler things could be done, like this:
>
>For example, a natural extension idea for core SCL
>is to allow people to write tuples of OTHER types
>than Atom_i and Term_i. These tuples could be,
>like, say, Man_1 and Father_2, ie ordinary
>TFOL predicates. In order to bring them in
>we would simply need to extend the abstract
>syntax and concrete syntaxes (the latter must
>then contain special markup). There is even
>no need to modify the current quantifiers. The
>Man_1 and Father_2 type of tuples would
>simply be disjoint from predicates as constants.

Why? If I follow you here, these seem remarkably close to the 'role' 
syntax for predicates, suggesting a further unification. BUt maybe I 
am not following you. Can you give a simple example?

Pat

>This is simple to do and will give us traditional
>FOL, but does not catch your idea of arbitrary overlap.
>For users, it would be a tad confusing though:
>some people would use "tuple predicates"
>while others would use "constant predicates",
>with no good reason as for why use one or
>another: this is a bit worrisome. We'd have
>to give good guidelines for usage, but still
>cannot completely avoid the possibility of confusion.
>
>Any ideas?
>
>Regards,
>           Tanel
>
>
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