[rules-users] Rules writing best practice?

[Swindells, Thomas]

Sounds like a sensible document to have.

The hints that I have picked up (which may or may not be accurate).

Make facts as small and isolated as possible - the more fields a fact has then the more rules that may be effected if any one of those fact fields are updated. From (and even more so nested froms) are particularly bad in this regards as any update to the fact requires the entire from expression to be re-evaluated.

I believe the order that conditions on a rule are ordered can make a big difference on how the graph is structured and which nodes can be shared in the graph. If you have a lot of conditions shared across multiple rules put them first and in the same order, this will allow them to be shared better (Can drools optimize this itself?).  Place the conditions which are going to restrict the result set the most first and the conditions which are likely to take longest to evaluate last (eg matches, complex evals).


I'm sure there are probably more suggestions and I'd also be interested in how much drools does this automatically for you (and if it doesn't currently how easy it would be to get it to do so?)

Thomas
> -----Original Message-----
> From: rules-users-bounces at lists.jboss.org [mailto:rules-users-
> bounces at lists.jboss.org] On Behalf Of Brice Figureau
> Sent: 09 February 2010 09:40
> To: Rules Users List
> Subject: [rules-users] Rules writing best practice?
>
> Hi,
>
> Is there a rules writing best practice document somewhere?
>
> I'm asking the question because as a newbie rule writer (which doesn't
> know anything about the underlying drools matching algorithm), I'm
> wondering if my rules will behave gracefully.
>
> For instance, I (ab)use a lot the from/accumulate to bring in the
> knowledge some external facts coming from some DAO.
> All my rules use one time or more the same "from
> dao.getInformationFromDatabase( <inserted fact> )" structure and I'm not
> sure the algorithm is smart enough to cache this information which is
> constant for a given inserted fact.
>
> Should I instead insert all this information as facts prior to the rules
> firing?
> --
> Brice Figureau
> My Blog: http://www.masterzen.fr/
>
> _______________________________________________
> rules-users mailing list
> rules-users at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users


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