I think Mark Nahabedian wrote:
> 
> It appears that I have some fundamental misunderstanding about when
> you use "?set" and when to use "$?set".  My misconception was that a
> variable needed to be prefixed with a $ if its value is a set.

No, it doesn't, but the manual certainly implies that it does.

I'm working on a book about Jess right now, and as work progresses I
have found places where the manual is misleading or doesn't make
sense. I'll be fixing those spots in the comming weeks.

> 
> Apparently a variable is only prefixed by a $ if it is meant to match
> more than one field in a fact in the left hand side of a rule.  Is
> that correct?

Yes.

> 
> I have a fact template
> 
>     (deftemplate equiv
>       (slot type)
>       (multislot set))
> 
> whose "set" slot will be a set (or list?) of atoms which identify
> faces, sides, etc.
> 
> To faces are "equivalent" (in the sense necessary for my application)
> if their identifying atoms are both present in the same such set of
> some "eqiv" fact.
> 
> I suppose I can test for such equivalence via
> 
>     (equiv (type face) (set $set))
>     (test (and (member$ ?thing1 $set) (member$ ?thing2 $set))
> 
> in the left hand side of a rule, and thus dispense with the apparently
> problematic use of the defquery.
> 

Sounds great (actually should be "$?set" but I think you knew that.)

---------------------------------------------------------
Ernest Friedman-Hill  
Distributed Systems Research        Phone: (925) 294-2154
Sandia National Labs                FAX:   (925) 294-2234
Org. 8920, MS 9012                  [EMAIL PROTECTED]
PO Box 969                  http://herzberg.ca.sandia.gov
Livermore, CA 94550

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