[rules-users] Is rule introspection available from the Drools API?

[Stephen Masters]

Also, is there a particular reason for using a stateless session? Depending on your application, using a stateful session could enable you to insert facts up front, meaning that you might not need to re-insert anything other than your ‘question' facts.

Steve


On 7 Jan 2014, at 13:04, Wolfgang Laun <wolfgang.laun at gmail.com> wrote:

> As you describe it, the fields of the fact objects shouldn't matter.
> 
> On 07/01/2014, milen igrachev <igrachev at abv.bg> wrote:
>> Hello,  initially i didn't give more details to keep my question short and
>> save time to the ppl that read it.  I actually believed that such
>> functionality might be covered and available and details would have just
>> prolong my question.
>>  Here is some additional information on why I am looking for such
>> functionality.  In my project I want to use Drools as external rule engine.
>> My project is not written in Java and the effort to transfer it is
>> inconsiderable.
> 
> I guess you mean "considerable".
> 
>> What I want to start using Drools for is a simple blackbox
>> of getting answers from a Stateless Drools  Session, most likely without any
>> need of reinference. Simply ask and get answered.  During the runtime of my
>> project there is a vast amount of information that can be considered as a
>> fact . However in  most of the cases what I need is to invoke a simple
>> ruleset that actually need like 1% of the  facts  that I currently know  at
>> any particular moment. So what I want to do is ask Drools "Hey I want to
>> invoke   ruleset, can you please tell  me what are the facts that it is
>> using so I can pass all of them, that I currently have?". Then after
>> receiving the answer I will  filter the 1% from the big picture and will
>> finally ask Drools to answer my question.
> 
> If these "rule sets" are unrelated with each other, you might put them into
> separater DRL files. Then the import list will tell you which facts this
> rule set needs, and so all you need is simple text processing...
> 
> -W
> 
>>  What I want to avoid is passing hundreds of instance/facts with hundreds
>> of fields that are actually never user.  Of course I realise that the rule
>> introspection that I am asking for is not my only option, I can create the
>> .drl metadata during  the ruleset definition. Some more ideas poped into my
>> head, so far, but the best solution for me seems to be if we can just call
>> Drools about that information and it return it as a straight answer.
>> 
>> That is why I am trying to identify if it is possible to recive the rule
>> metadata from Drools. At first I thought it could be available in  a snap of
>> a finger with some method calls, however now I am interested to see what is
>> the effort to make it happen.
>>  Hope it helps. Thanks for the support.
>>  Best Regards,  Milen
>> 
>> 
>> 
>> 
>> 
>> 
>> -------- Original Letter --------
>> 
>> From: Stephen Masters stephen.masters at me.com
>> 
>> About: Re: [rules-users] Is rule introspection available from the
>> 	Drools	API?
>> 
>> To: Drools List
>> 
>> Sent at: Tuesday, 2014, January 7 12:08:39 EET
>> 
>> 
>> 
>> 
>> 
>> 
>>   It may also be worth explaining exactly what you aim to achieve through
>> this and why. From what I have seen, most people who ask about introspecting
>> the LHS of rules via the API, don’t actually need to do that.
>> 
>> 
>> 
>> 
>> 
>> 
>>   Steve
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>>    On 7 Jan 2014, at 08:56, Wolfgang Laun <
>>     wolfgang.laun at gmail.com > wrote:
>> 
>> 
>> 
>> 
>>     Hi,
>> 
>> 
>> 
>> while you continue this line of research you might consider possible
>> 
>> ramifications and snags, and be prepared for them.
>> 
>> 
>> 
>> The syntax for writing LHS conditions is quite complex - it's more
>> 
>> complex than Java expressions, because the CE eval() alone will give
>> 
>> you (almost) all of that. Rule authors may also use DRL functions,
>> 
>> which could hide field access.
>> 
>> 
>> 
>> If *you* author the rules, you may be able to avoid the worst, but it
>> 
>> won't be a piece of cake.
>> 
>> 
>> 
>> Cheers
>> 
>> -W
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> On 07/01/2014, milen igrachev <
>>      igrachev at abv.bg > wrote:
>> 
>> 
>> 
>>      Hello thanks for the quick and precise answer!
>> 
>> 
>> I believe that the time difference will be a bit of a problem for the IRC
>> 
>> chat , but i will be online (channel: #drools user: igrachev) today and
>> will
>> 
>> try to check it often.
>> However big thanks for the support and the
>> 
>> willingness to help!
>> 
>> 
>> You are saying that the code is there, but is not public and documented.
>> 
>> Well being not public seems to be a problem, but do you
>> think it is
>> 
>> possible to give me an example with the official Drools "first rule" -
>> 
>> Sample.drl. The one that comes with the first Drools project.
>> So do you
>> 
>> believe it will be possible to paste me some code on how to retrieve the
>> 
>> information that this ruleset is using one fact of type Message
>> and two of
>> 
>> it's attributes -
>> status
>> and
>> message.
>> So just some code in a public
>> 
>> static void main (String [] args) will be great :), or any kind of
>> 
>> explanation :).
>> 
>> 
>> Once again thank you.
>> 
>> 
>> Have a nice day,
>> 
>> Milen
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> ----Original Letter----
>> 
>> From: Mark Proctor
>>       mproctor at codehaus.org
>> 
>> 
>> 
>> About: Re: [rules-users] Is rule introspection available from the Drools
>> 
>> 
>>         API?
>> 
>> 
>> 
>> To: Rules Users List
>> 
>> 
>> 
>> Sent at: Monday, 2014, January 6 16:05:33 EET
>> 
>> 
>> 
>> 
>> 
>> The code is there, but it’s not public and not documented, and the code can
>> 
>> be a little hard to understand - as it’s grown organically over the years.
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> You’ll need to cast and unwrap and look at member vars. Start on the Rule
>> 
>> and the lhs variable. You can always pop onto irc, with live questions,and
>> 
>> we’ll try and respond quickly.
>> 
>> 
>> 
>> 
>>       http://www.jboss.org/drools/irc
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> Mark
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> On 6 Jan 2014, at 09:51, milen igrachev
>> 
>>       igrachev at abv.bg
>> 
>>> wrote:
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>>       Hello,
>> 
>> 
>> 
>> 
>> 
>> 
>>       is there a way to introspect a Drools file from within java code?
>> 
>> 
>> 
>> 
>> 
>> 
>>       What I need is to be able to identify the facts and the fact
>> attributes
>> 
>> that are used in a given DRL file.
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>>       For example if I have a rule stored in a customer.drl DRL file within
>> my
>> 
>> project, containing the following definition:
>> 
>> 
>> 
>> 
>> 
>> 
>>       package myRulePackage
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>>       import org.rules.model.Customer
>> 
>> 
>> 
>> 
>> 
>> 
>>       import org.rules.model.Mambership
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>>       rule "is eligible customer"
>> 
>> 
>> 
>> 
>> 
>> 
>>          when
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>>          $c:Customer(status == "active")
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>>          Membership(customer == $c, type == "premium")
>> 
>> 
>> 
>> 
>> 
>> 
>>          then
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>>          $c.setEligibilityStatus(true);
>> 
>> 
>> 
>> 
>> 
>> 
>>       end
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>>       What i need is a way to understand that this ruleset customer.drl is
>> using
>> 
>> two fact types - Customer and Membership and three of their attributes -
>> 
>> Customer.status, Membership.customer and Membership.type.
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>>       I found some information on the internet that such functionality is
>> not
>> 
>> supported, however the information was a bit too old, so I decided to ask
>> 
>> again.
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>>       Big thanks for the support!
>> 
>> 
>> 
>> 
>> 
>> 
>>       Milen
>> 
>> 
>> 
>> 
>> 
>> 
>>       _______________________________________________
>> 
>> 
>> 
>> 
>> 
>> 
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>> 
>> 
>> 
>> 
>> 
>> 
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>> 
>> 
>> 
>> 
>> 
>> 
>>        https://lists.jboss.org/mailman/listinfo/rules-users
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
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>> 
>> 
>> 
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>> 
>> 
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>> 
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> 
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