Thanks for the response. This clears things up greatly. I guess what I am struggling with at this point is the best approach to applying the rules. I looked over the Conway example I began to use the DSL editor. This seems to be a "best approach" to defining the rules but still left me puzzled about the implementation. Should I create a wrapper class around my pojo's that I can implement business methods on to make applying the rules easier? Or should I load all the objects into working memory as you stated to represent a "relational model"? I can see pros and cons for both approaches and I can't seem to settle on which one would be best.

From: rules-users-bounces@lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of "Edson Tirelli" <tirelli@post.com>
Sent: Thursday, June 07, 2007 11:19 AM
To: "Rules Users List" <rules-users@lists.jboss.org>
Subject: Re: [rules-users] objects


   Chris,

   There is quite a few messages in the list archives about the "issues" of using nested objects.
   Best way is always to work with a "relational model" and assert all your objects to the working memory. One example would be:

rule R1
when
    $o : Order( requestStatus == RequestStatus.ACCEPT )
    Message( state == MessageState.RELEASING, order == $o )
then
    // do something
end

    Having said that, if you don't think it is justifiable to assert all objects into working memory because of just a few rules, you can also use the "from" CE:

rule R2
when
    $m : Message( state == MessageState.RELEASING )
    Order( requestStatus == RequestStatus.ACCEPT ) from $m.getOrder()
then
     // do something
end

    Finally, version 4.0 final will allow you to write the rule the way you wrote:

rule R3
when
    $m : Message( state == MessageState.RELEASING, order.requestStatus == RequestStatus.ACCEPT )
then
     // do something
end

   But it is important to note that the above will automatically generate an embedded eval() for you, that is exactly the same as doing:

rule R4
when
    $m : Message( state == MessageState.RELEASING, eval( order.getRequestStatus() == RequestStatus.ACCEPT ) )
then
     // do something
end

   And eval result needs to be constant over time.

   BTW, syntaxes used in R1, R2 and R4 are already supported in MR2/trunk. Syntax used in R3 above will be available in Drools 4.0 final release.

   []s
   Edson

2007/6/6, Chris Mathrusse <christopher.mathrusse@sybase.com>:
I'm new to the rules syntax and a bit frustrated with trying to learn it. I've
reviewed the docs but keep running into the same issue. I have a parent object,
Message, that contains an Order. An Order has a status that I want to test. So
looking at the documentation and taking my best guess I've created a rule as
follows:

rule "Order not Accepted"
when
  $m : Message( state == MessageState.RELEASING, order.requestStatus ==
RequestStatus.ACCEPT )
then
  ...
end

The problem is that when I start my application I get a compilation error.

Caused by:
org.drools.rule.InvalidRulePackage: [54,54]: unknown:54:54 mismatched token:
[@423,1899:1899='.',<69>,54:54]; expecting type RIGHT_PAREN[54,94]:
unknown:54:94 mismatched token: [@433,1939:1939=')',<37>,54:94]; expecting type
LEFT_PAREN
        at org.drools.rule.Package.checkValidity (Package.java:368)


So what am I missing? I know it has to be something simple with my understanding
of the syntax.

Thanks for the help...

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  Software Engineer - JBoss Rules Core Developer
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