[rules-users] RE: Need DRL authoring Help

[John.Tal at gxs.com]

Drools developers,

 

In our specific use case we have customers who need to be able to write
validation rules and NOT have to resort to writing them in Java.  Hence
our interest in using drools as an open source 'standard' to potentially
replace a proprietary rules engine we already have.

 

In the previous case I mentioned where I want to do this:

 

> *rule* "UCCnet_DVE_Depth_All"

>       *when*

>         catalogObject : CatalogObject( )

>         String s = catalogObject.getElementValue("depth");

>         *eval*( s == *null* || s == "" )

>       *then*

>             logWriter.logDebug("Package Depth is Blank");

> *end*

 

This is because potentially, in our use for data validation, there might
be 50 values we need to compare against.  Those values need to be on the
drools (not java) side of the world.  So getting the result of
catalogObject.getElementValue("depth") into a String variable and being
able to use String methods like indexOf or multiple || cases is much
more desirable than crossing from the rule back into the object by
having to call getElementValue 50 times.  There are numerous, other
cases, where the result of catalogObject.getElementValue need to be
saved into a local drools variable and evaluated multiple times without
encurring the overhead of multiple calls back into java.

 

Please consider enhancing drl syntax to support this use case.  Is there
a bug/enhancement process for me to follow to submit this functionality
request.

 

Thanks

 

John

 

 

 

 

Date: Thu, 5 Apr 2007 16:47:07 +1000

From: "Michael Neale" <michael.neale at gmail.com>

Subject: Re: [rules-users] RE: Need DRL authoring Help

To: "Rules Users List" <rules-users at lists.jboss.org>

Message-ID:

      <96ab3ced0704042347s130a4b46ma4a5b74fb45ef0d4 at mail.gmail.com>

Content-Type: text/plain; charset="iso-8859-1"

 

OK you are really bending what you would use rules for, I really
wouldn't recommend that. flattening the object model would allow you to
write rules over it, but as it stands, its just going to be a bit
difficult for you.

 

        catalogObject : CatalogObject( )

 

        *eval*( catalogObject.getElementValue("depth") == *null* ||

catalogObject.getElementValue("depth") == "" )

 

On 4/5/07, John.Tal at gxs.com <John.Tal at gxs.com> wrote:

> 

>  Ok,  Thanks for the help on the drl syntax.

> 

> So this works.

> 

> *rule* "UCCnet_DVE_Depth_All"

>       *when*

>         catalogObject : CatalogObject( )

>         *eval*( catalogObject.getElementValue("depth") == *null* ||

> catalogObject.getElementValue("depth") == "" )

>       *then*

>             logWriter.logDebug("Package Depth is Blank");

> *end*

> 

> But how do I get the drl parser to accept something like this:

> 

> *rule* "UCCnet_DVE_Depth_All"

>       *when*

>         catalogObject : CatalogObject( )

>         String s = catalogObject.getElementValue("depth");

>         *eval*( s == *null* || s == "" )

>       *then*

>             logWriter.logDebug("Package Depth is Blank");

> *end*

> 

> I am getting an Unexpected token 's'  InvalidRulePackage

 

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