Re: Knowledgework - Lisp Symbiosis

>>>>> On Mon, 05 May 2003 14:10:48 +0200, Miro Casanova <mcasanov@vub.ac.be> said:

    Miro> I have a little problem when trying to call a lisp expression inside a
    Miro> KW expression.

    Miro> This is a class I've implemented:

    Miro> (kw:def-kb-class facet ()
    Miro>    ((name :accessor name)))

    Miro> and this is a function to get instances of facet by comparing the
    Miro> value of the instance variable "name".

    Miro> (defun get-facet-obj (fct)
    Miro>    (kw:findall '?obj '(and (facet ?obj)
    Miro>                            (equal (name ?obj) fct))))

    Miro> I've solved the problem like iut's written below, but of course it's
    Miro> not the best solution (it's to get all the object of "facet" and then
    Miro> iterate with dolist and compare the instance variable with the
    Miro> argument given to the function).

    Miro> (defun get-facet-object (fct)
    Miro>    (let ((current-facet nil)
    Miro>          (facets-list  (kw:findall '?obj '(facet ?obj))))
    Miro>      (dolist (current-facet facets-list nil)
    Miro>        (if (equal (name current-facet) fct)
    Miro>            (return current-facet)))))

    Miro> I believe that the problem is that the call to (name ?obj) in the
    Miro> get-facet-obj function does not call "name", but instead it tries to
    Miro> equalize fct with the "structure" (the functor) (name ?obj) ! Of
    Miro> course I'm not sure of this.

    Miro> Anyone has any idea of what's happening?

I think you have more or less explained it to yourself. KnowledgeWorks
uses Prolog-style unification so you need to write your code something
like:

;;; untested
(defun get-facet-obj (fct)
   (kw:findall '?obj '(facet ?obj name ,fct)))

That is you can just pattern-match on the object.

;;; or more long-winded (also untested)
(defun get-facet-obj (fct)
   (kw:findall '?obj '(and (facet ?obj name ?name)
                           (= ?name ,fct))))

HTH

__Jason