[rules-users] Run a set of rules in a group B from a rule in agroup A

[Anstis, Michael (M.)]

Hi,

See below.
 
"executing a rule" is really two parts: LHS pattern matching (which
can't be stopped for a given RuleBase) and execution of the RHS (which
can be controlled by the agenda and truth maintenance).

I hope my time away hasn't led to me giving wrong advice.

Mike

-----Original Message-----
From: rules-users-bounces at lists.jboss.org
[mailto:rules-users-bounces at lists.jboss.org] On Behalf Of Thierry B
Sent: 21 January 2009 12:53
To: rules-users at lists.jboss.org
Subject: RE: [rules-users] Run a set of rules in a group B from a rule
in agroup A


Hello,

So if I've well understand :

- before calling fireAllRules(), Drools know for all rules (from any
group)
definied in DRL files, those which all patterns in the LHS of a rule are
matched, and those rules are placed on a agenda. 

At which moment exactly, Drools verified from a rule that all of its
pattern
in the LHS are matched, if it's before callling fireAllRules() ?

>>> Yes, LHS is evaluated on workingMemory.insert(o). A call to
fireAllRules() executes the activations on the agenda (i.e. RHS queued
as a consequence of LHS being matched on workingMemory.insert(o)).

- And fireAllRules() permit to execute all rules that are placed on
agenda

>>> Yes

- When using setFocus() from a java class or a rule, we can control the
order of rules to specify to execute rules from group B, and group C... 

>> I believe so.

- So it's not possible to tell Drools that we don't want to execute a
group
of rules if a rule A is not matched : in that group of rules : those
which
all paterns match LHS will be inevitably executed.

>>> Wrong. The rules won't be executed (read as activations - RHS -
won't be run) but you can't stop the LHS being evaluated.

All these points that I said, are exact?

Thanks :-)


Anstis, Michael (M.) wrote:
> 
> Please accept that my knowledge is based on 4.x and there might be
other
> alternatives in 5.
> 
> Rules are not "ran" but their patterns (LHS) evaluated as facts
> (objects) are inserted into Working Memory. When all patterns in the
LHS
> of a rule are matched activations are placed on the agenda for
execution
> of the consequence (RHS) when fireAllRules() is called (or other
> mechanisms to run what is on the agenda are invoked; such as
RuleFlow).
> So you could have rules in Group A cause Group B to receive the focus
> but it is the RHS's execution order you control and not the pattern
> matching - which will happen for Group A and Group B when facts are
> inserted into WM.
> 
> Look at Agenda Groups and RuleFlow. This should help.
> 
> With kind regards,
> 
> Mike
> 
> 

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