> fix. Try adding a test to verify that the users are in a unique order, i.e.
> alphabetical, with:
>
> (test (> 0 (str-compare ?user1 ?user2)))
Thanks, this works. However, I am looking for a more open solution and
still I wonder what is wrong on saying:
(not (or (people-toguether ?user1 ?user2) (people-toguether ?user2
?user1))
Jess complains saying: Bad slot value . at the line where the above
statement is written.
Thanks,
Diego
> From: D. Lopez-De-Ipina [mailto:[EMAIL PROTECTED]]
> Sent: Monday, May 21, 2001 8:48 AM
> To: [EMAIL PROTECTED]
> Subject:
>
>
> Hi all,
>
> I wonder if I can get some help with the following problem. I am trying to
> do event aggregation through Jess rules. For example, I want to determine
> when 2 users are spotted at the same time by a camera. For that I have
> defined a rule that looks like this:
>
> (defrule peopleToguether "Indicates when there are two people toguether"
> (TRIPevent (eventAtomID ?eventID1) (TRIPcode ?user1) (cameraID
> ?camera1))
> (TRIPevent (eventAtomID ?eventID2&~?eventID1) (TRIPcode
> ?user2&~?user1) (cameraID ?camera1))
> (targetPosition (eventAtomID ?eventID1) (x ?x1) (y ?y1) (z ?z1))
> (targetPosition (eventAtomID ?eventID2) (x ?x2) (y ?y2) (z ?z2))
> (test (> 5 (sqrt (+ (* (- ?x1 ?x2) (- ?x1 ?x2)) (* (- ?y1 ?y2) (- ?y1
> ?y2)) (* (- ?z1 ?z2) (- ?z1 ?z2))))))
> =>
> (printout t ?user1 " is in company of " ?user2 " " ?eventID1
> " " ?eventID2 " " ?camera1 crlf)
> (bind ?distance (sqrt (+ (* (- ?x1 ?x2) (- ?x1 ?x2)) (* (- ?y1 ?y2) (-
> ?y1 ?y2)) (* (- ?z1 ?z2) (- ?z1 ?z2)))))
> (printout t "Distance: " ?distance crlf))
>
> The problem is that given two facts, such as:
>
> "Diego seen by camera1" and "John seen by camera1"
>
> , the above rule fires twice, the first time associating ?user1 with Diego
> and ?user2 with John and the following time the other way around. A
> workaround to sort out this problem would be to assert a new fact to
> indicate that this rule has triggered and append to the LHS of the rule
> something like: (not (people-toguether ?user1 ?user2))
>
> However, I wonder if there is another more smarter way to do it. Moreover
> I can not fully comprehend why the rule fires twice and not simply
> once. Any reasons please?
>
> On the other hand, I tried to modify the above rule in order to sort out
> my problem by using the following OR logical patter in the lhs of the
> rule:
>
> (defrule peopleToguether "Indicates when there are two people toguether"
> (or (and (TRIPevent (eventAtomID ?eventID1) (TRIPcode ?user1) (cameraID
> ?camera1))
> (TRIPevent (eventAtomID ?eventID2&~?eventID1) (TRIPcode
> ?user2&~?user1) (cameraID ?camera1)))
> (and (TRIPevent (eventAtomID ?eventID2&~?eventID1) (TRIPcode
> ?user2&~?user1) (cameraID ?camera1))
> (TRIPevent (eventAtomID ?eventID1) (TRIPcode ?user1) (cameraID
> ?camera1))))
> (targetPosition (eventAtomID ?eventID1) (x ?x1) (y ?y1) (z ?z1))
> (targetPosition (eventAtomID ?eventID2) (x ?x2) (y ?y2) (z ?z2))
> (test (> 5 (sqrt (+ (* (- ?x1 ?x2) (- ?x1 ?x2)) (* (- ?y1 ?y2) (- ?y1
> ?y2)) (* (- ?z1 ?z2) (- ?z1 ?z2))))))
> =>
> (printout t ?user1 " is in company of " ?user2 " " ?eventID1
> " " ?eventID2 " " ?camera1 crlf)
> (bind ?distance (sqrt (+ (* (- ?x1 ?x2) (- ?x1 ?x2)) (* (- ?y1 ?y2) (-
> ?y1 ?y2)) (* (- ?z1 ?z2) (- ?z1 ?z2)))))
> (printout t "Distance: " ?distance crlf))
>
> When I parse this rule the Jess engine complains saying:
>
> Jess reported an error in routine Jesp.parsePattern.
> Message: Bad slot value .
> Program text: ( defrule peopleToguether "Indicates when there are two
> people toguether" ( or ( at line 166
>
> Could any of you please let me know what is not right in the OR pattern
> with nested ANDs? I don't get it. I hope my questions are not too basic.
>
> Thanks a lot for all your help in advance,
>
> -----
> Diego Lopez de Ipina
> http://www-lce.eng.cam.ac.uk/~dl231
>
>
>
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>
-----
Diego Lopez de Ipina
http://www-lce.eng.cam.ac.uk/~dl231
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