On Sep 7, 2007, at 1:01 PM, Hal Hildebrand wrote:
I guess I'm more than a little confused as to the "(templates $? ?t
$?)"
syntax.
Remember that the first time a variable is used, it matches
whatever's there, and subsequent uses of that same variable match
only whatever the first usage matched. The order of patterns can be
very important for this reason!
The above slot pattern matches "anything, followed by something (call
it "?t"), followed by anything else." In other words, this rule will
match each individual item in the list, one match for each item.
I would have expected that I could have rewritten the rule Wolfgang
provided to:
(defrule makeTransforms
?s <- (source (id ?id) (templates $? ?template $?))
So far, so good...
(not (transform (source ?id)))
This pattern says "If there are no 'transform' facts with the given
id," The first time this rule fires, there *will* be such a fact, so
it won't fire anymore, right? You need to write "If the fact this
rule will create doesn't exist yet" which would look like
(not (transform (source ?id) (template ?template)))
Worse however, regardless of whether I use the original
makeTransform rule
that Wolfgang proposed or the rewrite I did above, if I combine the
makeTransforms and your removeTransforms, I end up in a system
which goes
into an endless loop from simply asserting one source. Here's the
full
test:
...
(defrule removeTransforms
?t <- (transform (source ?id) (template ?t))
(not (source (id ?id)(templates $? ?t $?)))
=>
(retract ?t)
)
My bad. I made a mistake in the above: I used ?t as the name of both
the variable bound to the transform fact, as well as the variable
bound to the template slot. The second pattern never matches, as
there's no "templates" slot that contains 'transform' fact references!
The correct rule would be more like
(defrule removeTransforms
?t <- (transform (source ?id) (template ?template))
(not (source (id ?id)(templates $? ?template $?)))
=>
(retract ?t)
)
On 9/7/07 9:11 AM, "Ernest Friedman-Hill" <[EMAIL PROTECTED]> wrote:
Same idea:
(defrule removeTransforms
?t <- (transform (source ?id) (template ?t))
(not (source (id ?id)(templates $? ?t $?))
=>
(retract ?t))
On Sep 7, 2007, at 11:57 AM, Hal Hildebrand wrote:
Doh! That does work well and I'll certainly replace my cheesy
solution with
this, but one of the issues I'm dealing with is that the set of
templates
can change and I would like to ensure that as changes to the list of
templates occur, the corresponding transforms are asserted or
retracted.
Sorry, this is an additional constraint I would like to satisfy
that I
should have noted.
On 9/7/07 8:28 AM, "Wolfgang Laun" <[EMAIL PROTECTED]>
wrote:
Assuming that the absence of any "transform" fact with a "source"
slot
equal to the "id" slot of a new "source" fact is the criterion for
creating the "transform" facts:
(defrule makeTransforms
?s <- (source (id ?id)(templates $?templates))
(not (transform (source ?id)))
=>
(foreach ?temp $?templates
(assert (transform (source ?id) (template ?temp))))
)
kr
Wolfgang
Hal Hildebrand wrote:
I have a system where I need to ensure that for every member of a
list,
there is a fact which contains that member. For example, here's
my domain:
(deftemplate source (slot id) (multislot templates))
(deftemplate transform (slot source) (slot template))
What I would like is to write some rules that ensure that for
ever member of
the templates slot of a "source", I have a corresponding
transform. If I
assert:
(assert source (id 1) (templates (create$ a b c)))
I would like to see three facts asserted in response:
(assert transform (source 1) (template a))
(assert transform (source 1) (template b))
(assert transform (source 1) (template c))
I have accomplished this by creating an intermediary fact and
some rules
which essentially cycle through the list of templates in the
source,
asserting a transform for each. However, this just feels wrong.
It seems
like I should be able to express this without the intermediary
facts.
Perhaps this is where backward chaining would be useful? Or
perhaps I can
use the new "accumulate" CE? Or, have I already found the
solution using an
intermediary fact to cycle through the list of templates?
Any help/suggestions would be appreciated.
------------------------------------------------------------------
--
To unsubscribe, send the words 'unsubscribe jess-users
[EMAIL PROTECTED]'
in the BODY of a message to [EMAIL PROTECTED], NOT to the list
(use your own address!) List problems? Notify owner-jess-
[EMAIL PROTECTED]
------------------------------------------------------------------
--
-------------------------------------------------------------------
-
To unsubscribe, send the words 'unsubscribe jess-users
[EMAIL PROTECTED]'
in the BODY of a message to [EMAIL PROTECTED], NOT to the list
(use your own address!) List problems? Notify owner-jess-
[EMAIL PROTECTED]
-------------------------------------------------------------------
-
--------------------------------------------------------------------
To unsubscribe, send the words 'unsubscribe jess-users
[EMAIL PROTECTED]'
in the BODY of a message to [EMAIL PROTECTED], NOT to the list
(use your own address!) List problems? Notify owner-jess-
[EMAIL PROTECTED]
--------------------------------------------------------------------
---------------------------------------------------------
Ernest Friedman-Hill
Advanced Software Research Phone: (925) 294-2154
Sandia National Labs FAX: (925) 294-2234
PO Box 969, MS 9012 [EMAIL PROTECTED]
Livermore, CA 94550 http://www.jessrules.com
--------------------------------------------------------------------
To unsubscribe, send the words 'unsubscribe jess-users
[EMAIL PROTECTED]'
in the BODY of a message to [EMAIL PROTECTED], NOT to the list
(use your own address!) List problems? Notify owner-jess-
[EMAIL PROTECTED]
--------------------------------------------------------------------
--------------------------------------------------------------------
To unsubscribe, send the words 'unsubscribe jess-users
[EMAIL PROTECTED]'
in the BODY of a message to [EMAIL PROTECTED], NOT to the list
(use your own address!) List problems? Notify owner-jess-
[EMAIL PROTECTED]
--------------------------------------------------------------------
---------------------------------------------------------
Ernest Friedman-Hill
Advanced Software Research Phone: (925) 294-2154
Sandia National Labs FAX: (925) 294-2234
PO Box 969, MS 9012 [EMAIL PROTECTED]
Livermore, CA 94550 http://www.jessrules.com
--------------------------------------------------------------------
To unsubscribe, send the words 'unsubscribe jess-users [EMAIL PROTECTED]'
in the BODY of a message to [EMAIL PROTECTED], NOT to the list
(use your own address!) List problems? Notify [EMAIL PROTECTED]
--------------------------------------------------------------------
