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

Tue Jan 7 07:04:43 EST 2014

 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. 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. 
  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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