[rules-users] Drools - Doing Complex Stuff inside a Rule Condition or Consequence

[Michael Anstis]

Hi,

Which alternative you elect depends upon how *you* want to use Drools.

Rules externalise application logic from the code-base; the degree of the
separation is down to you.

If in doubt use Drools :) the flexibility of externalising various
operations could pay dividends when you come to maintain the application at
a later date.

If runtime performance of rules is important (i.e. using "from" could
represent an issue as implied by Mauricio Salatino) why not load facts into
Working Memory using a set of "bootstrap" rules first. This is in essence
equivalent to your proposed use of the Globals in your Alternative B (I
assume you'd use the Global to load facts into WM with a set of low salience
rules first).

If rules are to be authored by non-technical people you could look into
using a DSL to abstract some of the lower level syntax away form the rule
author.

Just my 2 cents in addition to Mauricio's - that makes 4 cents now - keep on
like this and you'll be able to retire early ;)

Cheers,

Mike

2010/11/29 Miguel Fernando Cabrera <mfcabrera at gmail.com>

> Hello everyone
>
> In my company we are planning to use Drools for couple of projects and we
> having some questions about the best way to use it
>
> My question is what should be and shouldn't be done inside a Rule
> Condition/Consequence. Given that we can write Java directly or call methods
> (for example From a Global object in the Working Memory).
>
> Example. Given a Rule that evaluates a generic Object (e.g. Person) have
> property set to true. Now, that specific propertie can only be defined for
> that Object going to the database (or going to a web service) and fetching
> that info. So we have two ways of implementing that:
>
> *Alternative A:*
>
>    - Go to the database and fetch the object property (true/false, a code)
>    - Insert the Object in the working memory
>    - Evaluate the rule
>
> *Alternative B:*
>
>
>    - Insert a Global Object that has a method that connects to the
>    database and check for the property for the given object.
>    - Insert the Object to eval in Working Memory
>    - In the rule, call the Global Object and perform the access to the
>    database
>
>
> Which of those is considered better? I really like A,  but sometimes B is
> more straightforward, however what would happen if something like a
> Exception from the Database is raised?* *I have seen the alternative B
> implemented  in the Drools 5.0 Book from Packt Publishing,however they are
> doing a mocking and they don't talk about the actual implications of going
> to the database at all.
>
> Thank you in advance,
>
> --
> Miguel Fernando Cabrera Granados
> http://mfcabrera.com
> "A los hombres fuertes les pasa lo que a los barriletes; se elevan cuando
> es
> mayor el viento que se opone a su ascenso." - José Ingenieros
>
> _______________________________________________
> rules-users mailing list
> rules-users at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.jboss.org/pipermail/rules-users/attachments/20101129/f43ecdd9/attachment.html