[rules-users] Event wait constraint syntax

[Kris Verlaenen]

Ajay,

Rule constraints can only reason on data in the working memory.  In
general there are two strategies for handling your problem then:

 1) The variable you want to access (in this case the request) is also
inserted in the working memory.  That way you could write something like:
  $r: Request( )
  Response( tag == $r.id )
Note that this would not work if you insert all requests simultaneously
into the same session (as any combination of request / response in the
session would trigger this process instance to continue, not only the
request related to this process instance.  So that means you would
execute each process instance in a separate session.

 2) You can also bind to the variables of your process instance by also
inserting your process instances in your session (for example using an
(on-entry/on-exit/normal) action in your process or by inserting it
through the api after starting it), so the rule constraint also has
access to that information.  Special logic makes sure that, if you are
evaluating a rule constraint inside the context of a specific process
instance, the "processInstance" variable is always bound to the current
process instance.
  processInstance: WorkflowProcessInstance()
  $r: Request( ) from processInstance.getVariable("request")
  Response( tag == $r.id )

We're still working on making that more user-friendly (advanced
execution mode will automatically insert/update the process instances
whenever necessary so you don't have to manage that yourself), so
suggestions in that area are welcome.

Thx,
Kris

Quoting Ajay.Gautam at rbs.com:

> I am trying to figure out how to specify the constraint for Event
> wait.
> 
> The rules flow diagram attached would be launched for each incoming
> "request". The request is set in a process scope variable (reqIn).
> Each request has a *tag* associated with it.
> 
> The event wait in question is waiting for a response event with the
> same tag value.
> 
> How would I create a constraint rule to match this?
> I guess the bigger question here is, how do I access the process
> scope request variable in the constraint?
> 
> Something like:
> 
> 
> RFQResponse (tag == reqIn.tag)
> 
> 
> 
> PS: When I try this, I get an error: "Unable to create restriction
> '[QualifiedIndentifierRestr: == reqIn.tag ]' for field 'tag' in the
> rule 'RuleFlow-Milestone-com.rbs.gbm.pm.RFQ-WorkFlow-21' : [Rule
> name='RuleFlow-Milestone-com.rbs.gbm.pm.RFQ-WorkFlow-21']"
> 
> 
> Any help / pointers would be highly appreciated.
> 
> Thanks
> 
> Ajay Gautam
> 
> 
> 
> 
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