Re: equality reasoning with functions and existentials?

The problem is that PowerLoom's just-in-time forward inference isn't comple=
te
enough here to pick up all that's required, and you have to run forward rul=
es
explicitly.  When you define an "inverse" for a relation, the required rules
are created by forward inference which isn't triggered by the JIT in this
case.  As an aside, inverse relations in a logic system like PowerLoom are
redundant and generally a bad idea for performance reasons.  Also, if you
declare an inverse on one relation, you shouldn't also do it on the inverse,
since it will generate redundant rules.  I know, PowerLoom should adivse us=
ers
on that, but currently it doesn't :-)

Anyway, after you do a "run-forward-rules" in the trace below, you get the
answer you are looking for.

Hans

STELLA(99): (clear-module pl-user)
:VOID
STELLA(100): (deffunction the (?i) :-> (?x Thing))
|f|THE
STELLA(101): (defrelation state-code (?s ?c)
  :axioms (inverse code-state state-code))
|r|STATE-CODE
STELLA(102): (deffunction code-state (?c ?p)
  :axioms (inverse state-code code-state))   ;; this is redundant and shoul=
d be avoided
|f|CODE-STATE
STELLA(103): (defrelation state-bird (?place ?birdtype))
|r|STATE-BIRD
STELLA(104): (defrelation population (?place ?pop))
|r|POPULATION
STELLA(105): (assert (exists (?x) (and (state-code (the ?x) "KS")
			  (population (the ?x) 2688418))))
(|P|(=3D (THE sk8884) sk8885) |P|(STATE-CODE sk8885 "KS") |P|(=3D (THE sk88=
84) sk8886) |P|(POPULATION sk8886 2688418))
STELLA(106): (assert (exists (?y) (and (state-code (the ?y) "KS")
			  (state-bird (the ?y) western-meadowlark))))
(|P|(=3D (THE sk8888) sk8889) |P|(STATE-CODE sk8889 "KS") |P|(=3D (THE sk88=
88) sk8890) |P|(STATE-BIRD sk8890 WESTERN-MEADOWLARK))
STELLA(107): (retrieve all (and (population ?x 2688418)
		   (state-bird ?y western-meadowlark)
		   (state-code ?x ?code)
		   (state-code ?y ?code)))
[2011-FEB-17 12:16:55.000 PL] Processing check-types agenda...
There is 1 solution:
  #1: ?X=3Dsk8886, ?Y=3Dsk8890, ?CODE=3D"KS"
STELLA(108): (retrieve all (and (population ?x 2688418)
		   (state-bird ?y western-meadowlark)
		   (code-state ?code ?x)
		   (code-state ?code ?y)))
There is 1 solution:
  #1: ?X=3Dsk8886, ?Y=3Dsk8890, ?CODE=3D"KS"
STELLA(109): (retrieve all (and (population ?z 2688418)
		   (state-bird ?z western-meadowlark)))
No solutions.

;;; so far, everything was as in the original formulation
;;; now we turn off the JIT and run forward rules explicitly:

STELLA(110): (unset-feature :JUST-IN-TIME-INFERENCE)
|l|(:JUSTIFICATIONS :EMIT-THINKING-DOTS)
STELLA(111): (run-forward-rules "PL-USER")
|L|TRUE
STELLA(112): (retrieve all (and (population ?z 2688418)
		   (state-bird ?z western-meadowlark)))
There is 1 solution:
  #1: ?Z=3Dsk8885
STELLA(113): =


>>>>> Dan Connolly <[email protected]> writes:

> I discovered powerloom the other day via a tweet
> =A0=A0http://twitter.com/danja/status/37660228791042048

> It looks pretty nifty.

> I'm trying to tell it:

> =A0state-code is unambiguous (i.e. its inverse is a function).
> =A0There's a place with state-code "KS" and population 28000.
> =A0There's also a place with state-code "KS" and state-bird western-meado=
wlark.

> and then ask it:
> =A0Is there a place with population 28000 and state-bird western-meadowla=
rk?

> The attached is my attempt. It's *almost* working, but not quite. I
> don't understand why not.

> Clues, please, anyone?

> --
> Dan Connolly
> http://www.madmode.com/
> untyped binary data, ,same-state.pl [Click mouse-2 to save to a file]
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