[rules-users] Drools Flow: Problem with constraint in (Wait) State node

[Alan.Gairey at tessella.com]

I have a simple rule flow of the form: Start -> Work Item -> Wait State -> 
Action -> End.

The handler for the work item launches a separate thread, and then 
completes. This thread inserts a number of facts into the (stateful) 
session's working memory; each fact ('SimpleFact') has a boolean property 
('complete') that is initially set false. Later on in the thread, the 
facts in memory are updated by setting their 'complete' properties to 
true.

I want the Wait State to hold execution of the rule flow until ALL the 
facts in memory have the 'complete' property set to true. My first attempt 
at setting the constraint was as follows:

forall(SimpleFact(complete == true))

With this constraint, the Action node executes straight after the 
completion of the Work Item. My next attempt for the constraint was:

exists(SimpleFact()) and forall(SimpleFact(complete == true))

With this constraint, the Action node executes as soon as the first 
instance of SimpleFact is inserted into the working memory.

So my question is: how do I specify the Wait State node constraint so that 
the rule flow only resumes once all the SimpleFact instances in working 
memory have their 'complete' property set to true?

(I have a simple project to demonstrate the problem if required.)

Many thanks,

Alan
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