[rules-users] Integrated User Configurable Rules Templates and DSL Example

[Wolfgang Laun]

I can answer one of the questions: how to achieve rule template
instantiation without spreadsheets for the actual parameters: Based on the
API  in the preliminary 5.0.0 relase, I wrote a few simple classes that let
you instantiate templates from Bean-style objects or property maps. I'm sure
that this would meet your requirements since you can control the contents of
the parameter objects any way you want, and you aren't stuck with a
spreadsheet for instantiation.

I've passed this on to the Drools development team two or three of weeks
ago, but I haven't seen it merged into the codebase yet. It definitly won't
make the first "official" 5.0 release that'S due any minute now, but there's
no reason why you shouldn't have these classes for experiments and planning,
now.

-W



On Thu, Apr 23, 2009 at 10:26 AM, Tim Langford <tim.langford at gmail.com>wrote:

> Hello All,
>
> I am very new to Drools and thinking about using it in a project.
> Apologies if these questions are naive - I have read the excellent
> documentation and written and run some examples but am still feeling a
> little lost.
>
> Due to the nature of the existing system the project will depend on we
> want to utilize the engine such that it operates and behaves like a
> 'function':
>
> 1) The system will always assert a single hierarchical object into the
> working memory of the required type.
> 2) Global variables will be attached to the working memory to provide
> visibility of system objects ; and also defined a set of return
> objects (to be retrieved by the host system after execution.
> 3) The rules will be execute to produce a set of results that will
> then be acted on externally by the host system.
>
> For example:
>
> We assert a 'Journey' (or another object) into a working memory with
> the following rule:
>
> rule "Journey No Charge Cancellation Option"
>    dialect "java"
>        when
>                # There are at least "{days}" days before the journey begins
>                $journey : Journey( )
>                eval(daysToDeparture($itinerary) > 30)
>        then
>                >toDebugLog("Journey 'no charge' cancellation.", logger);
>                >CancelOption option =
> instanceOfCancellationOption(kcontext.getRule().getName(),
> "CancelProcessor", 0);
>                >cancelOptions.add(option);
> end
>
>
> function CancelOption instanceOfCancellationOption(
>                String ruleName,
>                String targetProcessor,
>                Integer percentageBasedCharge) {
>
>                CancelOption option = new CancelOption();
>                option.setInvokingRule(ruleName);
>                option.setTargetProcessor(targetProcessor);
>
>  option.setDepositBasedChargePercentage(percentageBasedCharge);
>
>                return option;
> }
>
>
> The system must support different users from different companies - so
> these rules need to be 'templated'. We need to allow users to define
> their own instances and constraints on any of the template rules
> defined. Furthermore, they maybe from different countries so system
> must use the DSL functionality to wrap the rules and parameters in
> something meaningfully to them. Finally, we need to be to be able add
> constraints over the rules to ensure users do not misconfigure the
> rules and rules values (for example only a set of date ranges for
> canceling a journey that don't overlap). We don't want to use the
> spreadsheet templating mechanism. Rule configuration will have to be
> provided in our weblication (and backed by the guvnor).
>
> I could easily achieve this in pure java, groovy, etc. but would like
> to condsider drools due to 1) Wanting it to be a bit more dynamic than
> java (whilst not being so dynamic a user can easily make a mistake or
> get confused); 2) Getting the DSL features; 3) taking advantage of the
> all the rule versioning and management performed by the RMS.
>
> Sorry for the long introduction. My questions are:
>
> 1) Is Drools an overkill such functionality? (I am no expert).
> 2) Is there an example that uses templating (without spreadsheets) and
> DSL's somewhere? Does this work with the 'guvnor'? I have tested most
> Drools functionality, but don't seem to be able to get a handle on
> using all together to achieve this goal.
>
>
> Any insight or recommendations will be greatully recieved.
>
> Thanks
>
> Tim
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>
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