I’ve written this rule to be fired for Configuration object whose category is selected and subcategories are yet not selected. rule "select sub categories"             salience 50             no-loop             when                         $conf : Configuration($categoryId : $conf.getCategory().getCategoryId() != null, subCategories == null  )                         $subcats : ArrayList() from collect (Category ( parent1 == $categoryId ) )             then                         $conf.setSubCategories($subcats); end but it gives me following error. [34,56]: [ERR 101] Line 34:56 no viable alternative at input ')' in rule "select sub categories" in pattern Configuration [34,57]: [ERR 102] Line 34:57 mismatched input '.' expecting ')' in rule "select sub categories" in pattern Configuration [34,74]: [ERR 102] Line 34:74 mismatched input '!=' expecting 'then' in rule "select sub categories" in pattern Configuration Do I need to use “eval” around the “$conf.getCategory().getCategoryId()” part ?  Also in that case how do I get access to the property value ?  It doesn’t support something like this : $conf : Configuration($categoryId : eval( $conf.getCategory().getCategoryId() != null ), subCategories == null  ) Regards, Abhay ________________________________ From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Wendy Mungovan Sent: Tuesday, May 10, 2011 3:31 PM To: Rules Users List Subject: Re: [rules-users] FW: Basic rules question Abhay,   You can use the normal Java gets (if your object has them). when             $prod : Product ($prod.getMemory().getRam().getType() == "DDR") ... instead of $prod.getMemory()... you I think should also be able to use 'this.getMemory()....' (I have not tried these out to make sure) Wendy ________________________________ From: Abhay B. Chaware <Abhay.Chaware(a)kpitcummins.com&gt; To: Rules Users List <rules-users(a)lists.jboss.org&gt; Sent: Mon, May 9, 2011 11:56:42 PM Subject: Re: [rules-users] FW: Basic rules question OK. Another one.  How do I access and use a property of a member variable ( object ) of an object, in rules ? e.g.  in the same example, I need to check 1)  if a product of type ‘laptop’ is inserted in memory AND 2)  if the product’s MEMORY property ( object ) has an object of type DDR ram attached. In other words, here is the relationship of facts - PRODUCT has member variable MEMORY ( which is an object ) MEMORY has member variable RAM ( which is again an object ) RAM has member variable TYPE ( which should be equal to “DDR” ) From within rules ‘when’ part, how do I check if there is a PRODUCT inserted in memory whose MEMORY has a RAM of type DDR assigned ? Regards, Abhay Chaware Sr. Designer | KPIT Cummins Infosystems Ltd | Board: +91 020 6652 5000 | Extn: 2989  | abhay.chaware(a)kpitcummins.com |www.kpitcummins.com P Please consider the environment before printing this e-mail ________________________________ From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Michael Anstis Sent: Monday, May 09, 2011 4:27 PM To: Rules Users List Subject: Re: [rules-users] FW: Basic rules question Yes :) 2011/5/9 Abhay B. Chaware <Abhay.Chaware(a)kpitcummins.com&gt; Mike, What I meant was, There are say 10 objects of RAM in memory whose type is DDR.  Now my “Product” object has a member variable named “compatibleRAMs”, and I would like to set an arraylist containing these 10 objects to the “compatibleRAMs” variable of “Product” object in memory. I am reading about the “collect” which can be used to create collections from fact objects in memory.   Something like. When             $prod : Product (type==’laptop’) $compatibleRAMs : ArrayList() from collect (RAM (type == ‘DDR’)) Then             $prod.setCompatibleRAMs($compatibleRAMs); Am I on the right track ? -abhay ________________________________ From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Michael Anstis Sent: Monday, May 09, 2011 3:52 PM To: Rules Users List Subject: Re: [rules-users] FW: Basic rules question Abhay, Do you need a list? You can assign RAM to COMPUTERS with this:- when     $c : Computer( $type : type )     $r : RAM( compatibleWith == $type ) then    $c.addRAM( $r ); end This would add all RAM (in Working Memory) compatible with COMPUTER to computer. You could use a list of RAM as a Fact in WM and change your rule to use that:- when     $l : MyList( )     $c : Computer( $type : type )     $r : RAM( compatibleWith == $type ) from $l then     $c.addRAM( $r ); end Or you can define a rule to construct the list too:- when     $l : MyList( $t : typeRAM )     RAM( $c : $t ) then     $l.add( $r ) end I assume you'd need to differentiate different lists for different types; so I have shown use of "MyList" which could subclass ArrayList and have a "Type of RAM" attribute. Drools doesn't "do" generics. With kind regards, Mike 2011/5/9 Abhay B. Chaware <Abhay.Chaware(a)kpitcummins.com&gt; Wendy, Thanks for helping me out so far. I have another question. What if I have all my “RAM” objects inserted into working memory.   How should I write my rule’s “when” portion to get a collection of all the RAM objects matching type “DDR” ?  In other words, can I get collection of facts assigned to a variable and use it in the “then” part ? Thanks Abhay ================================== From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Wendy Mungovan Sent: Friday, May 06, 2011 5:47 PM To: Rules Users List Subject: Re: [rules-users] Basic rules question Q2:   So the rule would be something like: rule "RAM type"   when      $product: Product(type == "laptop");  then      //you are looking for the best way to set valid RAM types in the then part of the rule?     $product.setRamType("DDR");     //or    $product.setValidRamOptions( getValidRamOptions("DDR"));  end where getValidRamOptions would be a custom function included through 'import function' so you can then load the choices from some where else.  Or if RamOptions were an object in memory you could have a rule like: rule "RAM type"   when      $product: Product(type == "laptop");      $ramOptions: RAMOptions(type == "DDR");  then    $product.setValidRamOptions( $ramOptions.getList());  end Wendy ================================== Regards, Abhay Chaware Sr. Designer | KPIT Cummins Infosystems Ltd | Board: +91 020 6652 5000 | Extn: 2989  | abhay.chaware(a)kpitcummins.com |www.kpitcummins.com P Please consider the environment before printing this e-mail ________________________________ From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Wendy Mungovan Sent: Friday, May 06, 2011 5:47 PM To: Rules Users List Subject: Re: [rules-users] Basic rules question Abhay,   Q1:  I think that this will depend on how many different products you have.  If there is a small number it is more straight forward to have a rule for each one (so the 2nd option).  This allows all you logic to be in one place.  If there are a large number of products and writing a rule for each one is intractable you probably would want to look into some generalizations of the rules.  Is that helpful?   Q2: I'm not quite sure what you are getting at in Q2.  Are you trying to write validation rules or rules that are modifying the facts? Wendy ________________________________ From: Abhay B. Chaware <Abhay.Chaware(a)kpitcummins.com&gt; To: &quot;rules-users(a)lists.jboss.org&quot; <rules-users(a)lists.jboss.org&gt; Sent: Fri, May 6, 2011 4:59:46 AM Subject: [rules-users] Basic rules question Hi I am a newbie to rule based applications and trying to get the concept of rules. I have couple of questions about rules to start with, not specifically about Drools though. Q1 - Should rules be data/model specific or can/should they be generic or both ========================================================== e.g. If selected product “TYPE” is “laptop”, then category “RAM” should have all “DDR” type items compatible ( selecting items matching certain property ) OR If selected product is “IBM T42”, then category “RAM” should have “512MB DDR” , “1024MB DDR”, “2048MB DDR”  compatible. ( assigning individual items in rules ) OR Combination of both Q2 – How should be the data modeled in above case ========================================================== e.g. in product master, each item ( e.g. T40, T42 ) should have a “TYPE” ( e.g. desktop or laptop ) , all items in category “RAM” should have a “TYPE” ( e.g. DDR ) and then control the assignment of RAM options to the PRODUCT through Rule using “DDR” type ? OR in product master, each item ( e.g. T40, T42 ) should have a “TYPE” ( e.g. desktop or laptop ) , all items in category “RAM”  should have a “compatibleProduct” column ( e.g. desktop or laptop ) and control the assignment of RAM to PRODUCT through “dynamic” rules by selecting all the RAMs by passing the “TYPE” of the product to the database handler. Am I making my point clear ? Thanks Abhay This message contains information that may be privileged or confidential and is the property of the KPIT Cummins Infosystems Ltd. 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