[rules-users] Stateful session and non-existence of Facts

[Leonardo Gomes]

The email is big just because I tried to big as clear as possible, but it's
a quick reading, I promise!

No one?

Cheers,
Leo.

On Tue, Nov 24, 2009 at 10:42 PM, Leonardo Gomes <leonardo.f.gomes at gmail.com
> wrote:

> Hello,
>
> Regarding the session recreation, you're absolutely right, thanks!
>
> Anyway, I still have a problem and I believe it's more a design thing. Let
> me try to clarify it.
>
> I have different types of facts, let's say:
>
> * Types: FactA, FactB, FactC;
> * A stateful session with rules operating on them;
> * And a global variable, called output, which is a list of messages
> generated as consequences of those rules;
> * From time to time, I get notified that a fact of type FactA changed, then
> I have to:
>   - retract all facts of type FactA from my working memory
>   - reload them from the database (with java beans being created)
>   - reinsert them in that stateful session
>
> Now, let's say FactA(1) indicates a fact of type FactA and id = 1.
>
> - Then, in the beginning, I insert FactA(1) and FactA(2) in my working
> memory and fire the rules.
> - I have several rules operating on different types of facts, but I'm
> interested in one rule in particular which operates against FactA and reads
> something like:
>
> rule "test non existence"
> when
>     not FactA( id == 4 )
> then
>     output.add("there's no FactA id 4");
>
> - This rule is fired and the message is added to my output object.
>
> Later on, I have a notification that a FactA has changed, then I:
> - retract all FactAs from my working memory
> - clear all FactA-related messages from my output object
> - reload FactAs (let's say now I have FactA(1), FactA(3), but NOT FactA(4))
> - reinsert them in the WM
> - fire the rules
>
> The rule that checks that there's no FactA(4) doesn't refire. All other
> rules operating against FactA do, and since I had removed all FactA-related
> messages from my output object, this time I don't get the "there no FactA id
> 4" message in my output.
>
> It sounds like a situation for a stateless session, but I actually have
> several different rules, operating on different types of facts and don't
> want to refire all rules, just because a fact of type A changed.
>
> Maybe I should have an strategy of creating different sets of stateless
> sessions. I'm not sure. Advice is really welcome!
>
> Thanks again.
>
> Leo.
>
>
>
>
>
>
>
>
>
>
> 2009/11/17 Edson Tirelli <ed.tirelli at gmail.com>
>
>
>>    Leonardo,
>>
>>    First, I believer there is a misconception in your reasoning: creating
>> sessions is supposed to be much much cheaper than retracting all facts.
>> Creating a rulebase is heavier, because it requires compilation, but
>> creating a session is supposed to be very light by design. So, first thing
>> you should do is change that.
>>
>>    Regarding your question, if you insert:
>>
>>
>> SiteLanguage(language : languageCode)
>> t : SiteSpecialServiceType(type : specialServiceType)
>>
>>    The rule will activate and fire. If you don't, then the rule will not
>> match. That is how it is supposed to work.
>>
>>    Edson
>>
>> 2009/11/17 Leonardo Gomes <leonardo.f.gomes at gmail.com>
>>
>>>  Hi Guys,
>>>
>>> I have the following situation while running a stateful session with
>>> Drools 4.0.7:
>>>
>>> - I want to test that a fact with a given state doesn't exist;
>>> - It works fine
>>> - At a certain point I have to retract all facts and reinsert them at the
>>> stateful session - some of them actually changed and I don't want to
>>> recreate the session b/c it's expensive
>>> - Again the fact that didn't exist when I first created the session still
>>> doesn't exist
>>>
>>> ** Problem: This time the rule that verified the non-existence is not
>>> fired because I didn't insert any fact that would retrigger it.
>>>
>>> Rule example:
>>>
>>> rule "022"
>>>
>>> when
>>>
>>> SiteLanguage(language : languageCode)
>>> t : SiteSpecialServiceType(type : specialServiceType)
>>> not SiteLanguageSpecialServiceType(specialServiceType == type,
>>> languageCode == language)
>>> then
>>>                 <<consequence>>
>>> end
>>>
>>> How could I solve or workaround that?
>>>
>>>
>>> Thanks in advance,
>>> Leo.
>>> _______________________________________________
>>> rules-users mailing list
>>> rules-users at lists.jboss.org
>>> https://lists.jboss.org/mailman/listinfo/rules-users
>>>
>>>
>>
>>
>> --
>>  Edson Tirelli
>>  JBoss Drools Core Development
>>  JBoss by Red Hat @ www.jboss.com
>>
>> _______________________________________________
>> rules-users mailing list
>> rules-users at lists.jboss.org
>> https://lists.jboss.org/mailman/listinfo/rules-users
>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.jboss.org/pipermail/rules-users/attachments/20091126/6f8817c1/attachment.html