Hello Ernest,
Congratulations on the release of Jess 6.1a1. I just downloaded it and tried
to match a backward-chaining pattern to a defglobal (see message below). My
test rule looks like this:
(defrule test-rule
(have (possession_type ?*book*))
=>
(printout t "I have a book" crlf)
The defglobal ?*book* represents the Book.class java class:
Jess> (ppdefglobal *book*)
"(defglobal ?*book* = <External-Address:java.lang.Class>)"
The fact on the LHS is a backward-chaining definstance fact:
(ppdeftemplate have)
"(deftemplate MAIN::have extends MAIN::__fact \"$JAVA-OBJECT$
storyagents.storyworldontology.Have\"
(slot class (default <External-Address:jess.SerializablePD>))
(slot owner (default <External-Address:jess.SerializablePD>))
(slot owner_type (default <External-Address:jess.SerializablePD>))
(slot possession (default <External-Address:jess.SerializablePD>))
(slot possession_type (default <External-Address:jess.SerializablePD>))
(slot OBJECT (type 2048)))"
Now when I try to define the testrule, the following error message appears:
Jess> Jess reported an error in routine Node1TECT.call
while executing rule LHS (TECT).
Message: Error during LHS execution.
Program text: ( defrule test-rule ( have ( possession_type ?*book* ) ) = >
( printout t "I have a book" crlf ) ) at line 7.
at jess.Node1TECT.callNodeRight(jess/Node1TECT.java:54)
at jess.Rete.updateNodes(jess/Rete.java:890)
at jess.ReteCompiler.addRule(jess/ReteCompiler.java:87)
at jess.Rete.addDefrule(jess/Rete.java:708)
at jess.Jesp.addARule(jess/Jesp.java:1024)
at jess.Jesp.doParseDefrule(jess/Jesp.java:978)
at jess.Jesp.parseDefrule(jess/Jesp.java:901)
at jess.Jesp.parseSexp(jess/Jesp.java:159)
at jess.Jesp.parse(jess/Jesp.java:62)
at storyagents.LoadJessFileBehaviour.action(LoadJessFileBehaviour.java:59)
at jade.core.behaviours.Behaviour.actionWrapper(Behaviour.java:246)
at jade.core.Agent.mainLoop(Agent.java:1705)
at jade.core.Agent.run(Agent.java:1525)
at java.lang.Thread.run(Unknown Source)
Am I doing something wrong, or is the matching to defglobals still shaky?
Sander
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED]]On
> Behalf Of [EMAIL PROTECTED]
> Sent: zaterdag 23 maart 2002 16:20
> To: [EMAIL PROTECTED]
> Subject: Re: JESS: Backward chaining definstance facts
>
>
>
> I'm sorry, I guess I was writing in a kind of shorthand -- should have
> taken a bit more time. Of course, you can't have a bare function call
> as a slot value in a pattern, and as you observed, you can't use a
> function call at all in a backward-chaining pattern. I'd suggest that
> you use a defglobal to hold the Class object, but matching to
> defglobals is a little shaky in Jess 6.0. In the next release (which
> I've been promising "any day now" for several weeks, sorry) matching
> to defglobals will be fine, so that'd be one way to approach this.
>
>
> I think Sander Faas wrote:
> > Although I don't want to modify the objects in my ontology
> (as I mentioned
> > in my previous message), I couldn't resist to put this
> principle aside in
> > order to test if the trick works. The deftemplate of the
> have predicate now
> > looks like this:
> >
> > "(deftemplate MAIN::have extends MAIN::__fact \"$JAVA-OBJECT$
> > storyagents.storyworldontology.Have\"
> > (slot class (default <External-Address:jess.SerializablePD>))
> > (slot owner (default <External-Address:jess.SerializablePD>))
> > (slot ownerType (default <External-Address:jess.SerializablePD>))
> > (slot possession (default <External-Address:jess.SerializablePD>))
> > (slot possessionType (default
> <External-Address:jess.SerializablePD>))
> > (slot OBJECT (type 2048)))"
> >
> > The corresponding class:
> > class Have implements Predicate
> > {
> > PhysicalObject possession;
> > HumanBeing owner;
> > Class possessionType;
> > Class ownerType;
> > }
> >
> > (The setPossession and setOwner methods of this class update the
> > corresponding types by calling
> setPossessionType(possession.getClass()) and
> > setOwnerType(owner.getClass()) respectively)
> >
> > Now when I try to perform the trick:
> >
> > (defrule test-rule
> > (have (possessionType (class (call Class forName "Pencil"))))
> > =>
> > (printout t "I have a pencil" crlf)
> > )
> >
> > I receive the error message "Bad slot value".
> >
> > When I try:
> > (have (possessionType (call Class forName "Pencil")))
> >
> > the same error shows up, and:
> > (have (possessionType ?pt&=(call Class forName "Pencil")))
> >
> > results in "Can't use funcalls in backchained patterns MAIN::have"
> >
> > Any ideas would be greatly appreciated.
> >
> > Sander
> >
> >
> >
> > > -----Original Message-----
> > > From: [EMAIL PROTECTED]
> > > [mailto:[EMAIL PROTECTED]]On
> > > Behalf Of [EMAIL PROTECTED]
> > > Sent: dinsdag 19 maart 2002 20:11
> > > To: [EMAIL PROTECTED]
> > > Subject: Re: JESS: Backward chaining definstance facts
> >
> > <cut>
> >
> > > OK, anyway, the trick is to use
> > >
> > > (have (possession-type (class (call Class forName
> > > "package.pencil"))))
> > >
> > > where you've got "(have (possession ?pencil <of type pencil>))"
> > > below. Then the need-have fact should have the posession-type slot
> > > filled in with the appropriate class object, which you can use to
> > > synthesize the "pencil" object and "have" fact.
> >
> > <cut>
> >
> >
> > --------------------------------------------------------------------
> > To unsubscribe, send the words 'unsubscribe jess-users
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> > --------------------------------------------------------------------
> >
>
>
>
> ---------------------------------------------------------
> 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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