[rules-users] global as link to DB: different results

[Wolfgang Laun]

If the "donator" isn't a fact, it's not visible to the engine.

Globals are OK on the RHS and as a provider for constant (!) data used as
stand-in for literals on the LHS. Other than this: beware!

-W


2011/10/31 Michael Anstis <michael.anstis at gmail.com>

> I thought use of the "from" keyword allowed you to reason over facts
> (potentially) not in WM. I believe the OP's example is mentioned in the
> docs?
>
> sent on the move
>
> On 31 Oct 2011 15:08, "Wolfgang Laun" <wolfgang.laun at gmail.com> wrote:
>
>> Globals cannot to be used - directly or indirectly - as objects that
>> should trigger
>> the firing of rules. It is only insert, modify or update, and retract
>> that cause (re-)evaluation of LHS conditions.
>>
>> -W
>>
>>  On 31 October 2011 15:05, elsdestickere <elsdestickere at yahoo.com> wrote:
>>
>>> Hi,
>>>
>>> I read docs about global and Hibernate to access your DB from the rules.
>>> I tried something simular for in memory DAO's.
>>> But some rules fire ("WM" in RHS) as the DAO has 3 items, but others
>>> ("dao"
>>> in LHS) don't, how is that possible?
>>>
>>> global RepositoryFactory repFact;
>>> rule "dao"
>>>    when
>>>       k : Customer(  ) from repFact.getCustomerRepository().findAll();
>>>    then
>>>        System.out.println( "Drools "+drools.getRule().getName()+": "
>>> +k.getName());
>>> end
>>> rule "WM"
>>>    when
>>>       k : Customer(  ) ;
>>>    then
>>>        System.out.println( "Drools "+drools.getRule().getName()+": "
>>> +k.getName()+" + size:
>>> "+repFact.getCustomerRepository().findAll().size());
>>> end
>>> ...
>>> RepositoryFactory repFact = Registry.getRepositoryFactory();
>>> ksession.setGlobal("repFact", repFact);
>>> ...
>>> CustomerRepository customerRepo = Registry.getRepositoryFactory()
>>>                                .getCustomerRepository();
>>> customerRepo.add(tom);
>>> customerRepo.add(elise);
>>> customerRepo.add(bert);
>>> ksession.insert(bert);
>>> ksession.fireAllRules();
>>>
>>> ...
>>> Output:
>>> Drools WM: Bert + size: 3
>>>
>>> br,
>>> Els
>>>
>>>
>>> --
>>> View this message in context:
>>> http://drools.46999.n3.nabble.com/global-as-link-to-DB-different-results-tp3467897p3467897.html
>>> Sent from the Drools: User forum mailing list archive at Nabble.com.
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>>>
>>
>>
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