Jess and most other production rule languages do not have Herbrand terms
that prolog-like languages use to model tree-structured facts. In your
case you can simply flatten your data model to a single fact with 2 x
and 2 y coordinates, as Hal suggests.
In more complex cases you may want to assert several linked facts -- but
your rules may need several patterns and tests to put th pieces back
together again.
Levent Kent wrote:
Hi,
I am a new user fo Jess and try to get some understanding for the engine.
I cant understand why the code below does not work.
(deffacts graph-links3
(link3 (gnode3 0 0) (gnode3 2 1))
)
Here, I am trying to describe links of nodes with 2 coordinates.
How should I do that?
I also tried this version:
(deftemplate gnode (slot x) (slot y))
(deftemplate link (slot start) (slot end))
(deffacts graph-links
(link (start (gnode (x 0) (y 0))) (end (gnode (x 2) (y 1))))
(link (start (gnode (x 2) (y 1))) (end (gnode (x 1) (y 2))))
(link (start (gnode (x 2) (y 1))) (end (gnode (x 2) (y 0))))
(link (start (gnode (x 2) (y 0))) (end (gnode (x 1) (y 1))))
(link (start (gnode (x 1) (y 1))) (end (gnode (x 0) (y 2))))
(link (start (gnode (x 0) (y 2))) (end (gnode (x 2) (y 3))))
(link (start (gnode (x 1) (y 2))) (end (gnode (x 1) (y 3))))
)
I am always geetıng the error message:
Jess reported an error in routine Funcall.execute
while executing (gnode3 0 0)
while executing assert from deffacts MAIN::graph-links3
while executing (reset).
Message: Undefined function gnode3.
or
Jess reported an error in routine Funcall.execute
while executing (gnode (x 0) (y 0))
while executing assert from deffacts MAIN::graph-links
while executing (reset).
Message: Undefined function gnode.
Some little help would save me from confusion.
I hope this message will be accepted by the mailing list, because I am not
sure if my messages are delivered successfully.
Thanks,
Levent
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