[SCL] Headers and bodies

[Bill Andersen]

On Nov 27, 2003, at 2240, John F. Sowa wrote:

> Pat,
>
> When I said that I would prefer to have a very small
> (say 2) number of Boolean operators in the SCL core,
> I meant that as a preference.  If you and Chris want 5,
> I can live with it, but 5 just sounds rather arbitrary.

While we're on the subject, I find that it comes up often in practice 
that one
wants to write axioms

   (<= something
       something-else)

and

   (=> something
       something-else)

as a matter of clarity.  The first case comes up a lot when one wants 
to write
axioms that positively define <something> and the second comes up when 
one wants
to (negatively) constrain <something>, i.e., that <something-else> is 
of the form
(not ...).  Seen another way, the first, when <something> is an atom, 
is a style
that Prolog people like, while the second is more natural when one 
thinks of
if-then kinds of rule.

I know there's no semantic difference between the two and I'm not sure 
if such
aesthetic considerations ought to play a role (I suspect they do 
already else we
could get by with two boolean operators or just sheffer stroke if we 
want to be
really concise).

How hard would it be to modify the abstract syntax to allow for defined 
operators
if we don't want to admit what would be otherwise perceived as 
superfluous ones
into the base document?

   .bill

--
Bill Andersen (andersen at ontologyworks.com)
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