[rules-users] API for reading and writing rules

kurrent93 kurrent93 at gmail.com
Tue Mar 19 13:36:43 EDT 2013 

thanks Steve, that would be greatly appreciated!

I've just been reading up about Antlr and DSLs - all new territory.

Here is a sample rule that we would be likely to generator.
1.|rule "close old trades"2.|    dialect "mvel"3.|    when4.|        t :
Tick( ) over window:length (1)5.|        closeMe : TradeOrder(
orderOpenTime before [2m] t.tickTime )6.|    then7.|        closeMe.setStatus(
OrderStatus.CLOSING );8.|        update( closeMe );9.|
        modifiedOrderList.add(closeMe);10.|end


On Tue, Mar 19, 2013 at 6:15 PM, Stephen Masters [via Drools] <
ml-node+s46999n4022889h78 at n3.nabble.com> wrote:

> Obviously I don't know what your rules and model look like, but it's worth
> considering. The DSL templates are designed to be parsed relatively easily,
> with a single clause per line, so although they are not always that
> readable (if they're generating a lot of DRL code), they do the job of
> providing a template reasonably well.
>
> My number one tip working with them is to create a simple unit test class
> which creates a knowledge base from the DSL and a simple example DSRL. That
> way the unit test works as a compiler for your DSL/DSRL and lets you know
> when you mess up. You can of course build more complex tests, but it's
> always good to have that minimal test there to confirm that things are at
> least compiling.
>
> If you're able to provide an example (perhaps slightly anonymised) DRL
> rule that your application could be generating, then I'd be happy to have a
> go at knocking up a simple straw man DSL which could generate it. It may
> not be quite what you need, but it could be a useful starting point.
>
> Steve
>
>
> On 19 Mar 2013, at 16:34, kurrent93 <[hidden email]<http://user/SendEmail.jtp?type=node&node=4022889&i=0>>
> wrote:
>
> Thanks Steve
>
> Yes that sounds like a way forward. I'll do some research on creating a
> dsl.
>
> Any pointers are appreciated.
>
> Cheers
>
>
> On Tue, Mar 19, 2013 at 5:20 PM, Stephen Masters [via Drools] <<a
> href="x-msg://437/user/SendEmail.jtp?type=node&amp;node=4022888&amp;i=0"
> target="_top" rel="nofollow" link="external">[hidden email]> wrote:
>
>> If you are going to generate DRL, you need to parse your model into a
>> much more general language and parse that language back into your model.
>> The APIs don't save you from doing this, they just mean that you interact
>> with an API to generate the code, and get some validation, rather than just
>> outputting strings. Additionally, I suspect that you would need to use APIs
>> that are not really intended for public consumption and may change any time
>> you update Drools.
>>
>> A DSL defines a template for your own language, for which you define
>> mappings to DRL. You can write DSLR code using that DSL syntax, instead of
>> DRL. Given that you write the DSL yourself, it should be specific to your
>> requirements and relatively simple to generate in many cases (depends on
>> your model of course). Additionally, given that you would be using it as an
>> intermediate language, you could write a DSL to be parsed easily, rather
>> than the usual natural language style.
>>
>> So your code just needs to generate and read your simplified language.
>> Drools deals with parsing your DSLR code into rules. And you have your own
>> stable language. i.e. You can update Drools with minimal impact to your
>> application.
>>
>> It depends mostly on how flexible your rules generation needs to be. If
>> the customers will be defining values to be dropped into relatively fixed
>> rule structures, then doing this could be pretty simple.
>>
>> Steve
>>
>>
>> On 19 Mar 2013, at 15:54, kurrent93 <[hidden email]<http://user/SendEmail.jtp?type=node&node=4022887&i=0>>
>> wrote:
>>
>> thanks Stephen
>>
>> My knowledge of DSLs is very limited. But isnt the problem still parsing
>> in the DRL into the DSL? I dont really understand how a DSL helps - but
>> that is probably due to my lack of knowledge here.
>>
>>
>> On Tue, Mar 19, 2013 at 4:41 PM, Stephen Masters [via Drools] <<a
>> href="<a
>> href="x-msg://429/user/SendEmail.jtp?type=node&amp;amp;node=4022886&amp;amp;i=0">x-msg://429/user/SendEmail.jtp?type=node&amp;node=4022886&amp;i=0"
>> target="_top" rel="nofollow" link="external">[hidden email]> wrote:
>>
>>> Depending on your model, it may be better to create a DSL as an
>>> intermediate language. That way you have a simplified language, which you
>>> control, to parse in and out, which could be tuned to your own domain model.
>>>
>>> Steve
>>>
>>>
>>> On 19 Mar 2013, at 14:36, kurrent93 <[hidden email]<http://user/SendEmail.jtp?type=node&node=4022885&i=0>>
>>> wrote:
>>>
>>> HI David
>>>
>>> Yes we are also looking into rule templates.
>>>
>>> We have come up with - what we believe - is a very
>>> natural, intuitive and visually appealing way to author rules. And it is
>>> tailored for our specific domain.
>>>
>>> One significant aspect of our work is that we are present drools
>>> authoring to end users - customers - rather than business users. Hence
>>> the importance of crafting a specialized UI, rather than the generic UI of
>>> Guvnor.
>>>
>>> And FYI - are also including in the design some UI elements, for a
>>> future version, that will use Drools Chance features.
>>>
>>> Can you point me to documentation - and ideally - samples around using
>>> APIs for the descriptor level?
>>>
>>> Thanks
>>>
>>>
>>>
>>>
>>> On Tue, Mar 19, 2013 at 3:11 PM, Davide Sottara [via Drools] <<a
>>> href="<a href="<a
>>> href="x-msg://398/user/SendEmail.jtp?type=node&amp;amp;amp;node=4022881&amp;amp;amp;i=0">x-msg://398/user/SendEmail.jtp?type=node&amp;amp;node=4022881&amp;amp;i=0"><a
>>> href="x-msg://398/user/SendEmail.jtp?type=node&amp;amp;node=4022881&amp;amp;i=0">x-msg://398/user/SendEmail.jtp?type=node&amp;node=4022881&amp;i=0"
>>> target="_top" rel="nofollow" link="external">[hidden email]> wrote:
>>>
>>>> As a RETE network is being created, DRL Rules are parsed into an
>>>> internal "descriptor" structure (a high level AST)
>>>> and then compiled into a RETE.
>>>>
>>>> There are "APIs" to create rules at the descriptor level: this can then
>>>> be "dumped" back into DRL.
>>>> To work at the DRL level directly, it's common to use parametric
>>>> "templates".
>>>>
>>>> If your internal (meta)model is object oriented, you could consider
>>>> using DRL rules to write the translators :)
>>>>
>>>> Davide
>>>>
>>>> p.s. could you provide some more information about your use case? I'm
>>>> doing some research on rule authoring
>>>> environments right now. Thanks!
>>>>
>>>>
>>>>
>>>>
>>>> On 03/19/2013 09:54 AM, Michael Anstis wrote:
>>>>
>>>> Rules are DRL that is a String.
>>>>
>>>> Where and how you choose to store the String is up to you.
>>>>
>>>> Please try to explain what you want to achieve a little more.
>>>>
>>>> On 19 March 2013 12:49, kurrent93 <[hidden email]<http://user/SendEmail.jtp?type=node&node=4022878&i=0>
>>>> > wrote:
>>>>
>>>>> HI all
>>>>>
>>>>> Is there any samples or documentation for reading and writing of rules?
>>>>>
>>>>> The user case is we are trying to build a custom Rule Editor, and thus
>>>>> would
>>>>> like to write and read rules to/from our beans.
>>>>>
>>>>> Thanks
>>>>>
>>>>>
>>>>>
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>>>>
>>>>
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