[rules-dev] Firing rules only if action causes updates to data?

[Peter Lin]

simple

rule x:

if
  a = 5
  b = 3
  c != 0
then
  c = 0

keep in mind that using negation NOT means that condition does not exist. In
other words, if I have this rule

rule y:
if
  a = 5
  b = 3
  not c = 0
then
  c = 0

rule y means a is 5, b is 3 and no c is zero.  Say i assert 100 objects to
the working memory and 1 of them has c = 0. it means rule y would never
fire, since there is a fact that satisfies "not c = 0".

hope that helps

peter

On 2/27/07, Premkumar Stephen <prem18 at gmail.com> wrote:
>
> Hi Dev team,
>
> Its been fascinating to watch the growth of this tool. Here is my
> question:
>
> Rule x:
> if
>    a = 5
>    b = 3
> then
>    c = 0
>
> Now, I have written this rule to run when a = 5 and b =3. But actually, I
> would like it to ideally run when a = 5 and b = 3 and c != 0
>
> Now, does the second scenario lead to any savings. In Ilog, the second
> scenario will result in the rule NOT being added to the agenda whereas it
> would in the first.
>
> I cannot code the second scenario into the rule as the rule ( as seen in
> UI) needs to match the requirements version ( in Doors) and they do not want
> to add these to the requirements. I would just like to make the second
> version for performance. We have noticed that less number of rules would
> fire.
>
> Now, if a = 5, b = 3 and c = 0, is there a way Drools can look at it and
> say, let me not fire this rule since there is no practical use anyways.
> If not, what are the ways to automate not firing rules in scenarios where
> action does NOT cause updates to data.
>
> Thanks!!
>
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>
>
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