[SCL] Headers and bodies

[pat hayes]

>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.

A concrete syntax could have two forms of the implication as long as 
they both parse to the SCL abstract-syntax implication. Then it 
swould be up to the parser for that syntax to make sure there was no 
abmbiguity, etc.

>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?

The only issue is that we would need a syntax for defining new 
operators. If someone could suggest a simple, easy-to-implement, 
easy-to-understand-and-state such notation, please by all means do 
so. BUt if its more complicated than just including a couple of new 
operators, then I suggest we just include all the ones that anyone 
wants.

Pat


>
>   .bill
>
>--
>Bill Andersen (andersen at ontologyworks.com)
>Chief Scientist
>Ontology Works, Inc. (www.ontologyworks.com)
>1132 Annapolis Road, Suite 104
>Odenton, Maryland 21113
>United States
>Office: 410-674-7600
>Mobile: 443-858-6444


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