[rules-users] Local Variable

[Wolfgang Laun]

Just  to  add another option:

A variable to set in one and to use in another consequence can also be
a static field in some Java class, with (or without - huh!) setter and
getter.

However, no matter which technique one chooses, setting such a
variable in rule A and using its value in rule B creates two
dependencies:
  - the temporal dependency that rule A must execute before rule B
  - the logical dependency that an execution of rule A with some
specific set of facts must "match" the execution of rule B; in other
words, one needs to make sure that there is no confusion among
multiple executions of rule A  and rule B.

Only a dynamically created object, inserted logically or not, has a
chance to handle these dependencies, with fields in addition to the
"value" to be passed on identifying the context, i.e., one or more
facts participating in the firing of A.

Anything else is playing with fire.

-W




On 05/10/2012, Davide Sottara <dsotty at gmail.com> wrote:
> The concepts of "local" and "accessible to another rule" are a little bit
> conflicting :)
> This said, as others have already pointed out, there are many ways to
> achieve this result, including:
>
> - globals
> - chaining : rule A inserts a fact and "pushes" it (also) into rule B,
> which
> reacts to its insertion
> - facts : both rule A and B see a fact in the WM and match/modify it
> - queries : rule A inserts a fact and rule later B pulls it from the WM
>
> If you could provide some more details about what you're trying to do, we
> may be able to recommend the best approach. One thing for sure: the RHS of
> different rules live in different scopes, so there is no way
> to make a LOCAL variable (i.e. declared locally in a RHS) visible to other
> rules' RHSs.
>
> Best
> Davide
>
>
>
> --
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