Taxonomic reasoning

I am trying to understand how taxonomic reasoning works.  Consider the
following class definitions:

(in-package :lisa-user)

(defclass mysuper ()
  ())

(defclass mysub (mysuper)
  ())

I would like to write a rule that matches only mysuper facts, and a
different rule only for mysub facts, i.e. I don't want the rule for
mysuper to also match mysub:

(defrule match-mysuper ()
  (mysuper)
  =>
  (format t "~&Matched MYSUPER~%"))

(defrule match-mysub ()
  (mysub)
  =>
  (format t "~&Matched MYSUB~%"))

If I understand correctly, this should do what I want if I set
consider-taxonomy to nil.  But LISA works in a different way.  Here is
what happens with the default of t for consider-taxonomy (see my other
message):

LISA-USER> (reset)
T
LISA-USER> (assert (mysuper))
#<FACT F-1, MYSUPER, CF is 0.000>
LISA-USER> (assert (mysub))
#<FACT F-2, MYSUB, CF is 0.000>
LISA-USER> (run)
Matched MYSUPER
Matched MYSUPER
Matched MYSUB
3

And here is what happens when I toggle consider-taxonomy:

LISA-USER> (reset)
T
LISA-USER> (setf (consider-taxonomy) nil)
NIL
LISA-USER> (assert (mysuper))
#<FACT F-1, MYSUPER, CF is 0.000>
LISA-USER> (assert (mysub))
#<FACT F-2, MYSUB, CF is 0.000>
LISA-USER> (run)
Matched MYSUPER
Matched MYSUPER
Matched MYSUB
3
LISA-USER> 

Setting consider-taxonomy has apparently non effect.  Is this the
expected behavior?  Are my rules correct?  If not, do I have to
rewrite match-mysuper like this?  It feels quite kludgey.

(defrule match-mysuper ()
  (mysuper)
  (not (mysub))
  =>
  (format t "~&Matched MYSUPER~%"))

I am using CMUCL Snapshot 2005-09 (19B) under Linux with the latest
LISA CVS sources.


Paolo
-- 
Lisp Propulsion Laboratory log - http://www.paoloamoroso.it/log


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