[rules-users] Getting started with Drools Fusion

[Edson Tirelli]

   Hi Tina,

   I might look daunting at first, but I hope once you start using it, you
will realize how powerful the concept of enabling CEP for rules and
processes is and how simple that becomes in Drools as compared to
integrating heterogeneous products for the same task.

   I recommend you read the Drools Expert documentation as well, as Fusion
features are additions to the overall Expert features and syntax.

   Regarding your questions: drools does not handles persistence by itself.
It delegates to the application to decide what to do with them. You can of
course persist individual events in a database or disk, or you can persist
drools session snapshots if that fits better your application model.

   Sliding windows are always based on the current time or latest event, but
Drools offers the complete set of 13 temporal operators and their negations.
So you can reason over times A and B. For instance, you want to check that
event Eb happened between 10s and 30s after Ea. You can write that as:

$ea : EventA()
$eb : EventB( this after[10s,30s] $ea )

   So that creates a arbitrary "windows of interest" that are not based on
the current time, but otherwise anchored on each EventA that is received by
the engine.

   Hope it helps,

   Edson

2010/5/7 Tina Vießmann <tviessmann at stud.hs-bremen.de>

> Hello everybody :)
>
> I'm completely new to the Drools universe. I've discovered Drools, or more
> specifically Drools Fusion, by looking for a powerful CEP engine.
> I've read the DF user guide and came up with some issues about DF features.
> It would be great, if anyone can give me some explanations and/or refer to
> different information sources.
>
> My questions:
>
> 1. Persistence of events:
> I know that DF can store events explicitly and implicitly. But does it
> store events in persistent (e.g., I can continue my computation after a
> reboot)? If it does, how are the events stored?
>
> 2. Sliding windows:
> It's written that a window contains the last X events/the event occurred
> in the last X time units. Is it somehow possible to specify a window for
> process only old events - which does not catch up to the latest event?
> (Lets assume we have the times A, B and C with: A < B < C  and  C ==
> current time. Is it possible to specify a window that process events
> occurred between A and B?)
> So are more complex windows like described in chapter 7 of the book 'Event
> Processing in Action' (see http://www.manning.com/etzion/) possible?
>
>
> Are there any (step-to-step) tutorials / how-tos about simple DF programs?
>
>
> In case my questions are stupid because they can be answered when knowing
> Drools, but I've got absolute now experience using Drools. At the moment I
> kind of have the feeling, Drools is a little bit too complex for just
> using to implement CEP applications...
>
>
> Thanks for any help! :)
>
> Tina
>
>
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>



-- 
 Edson Tirelli
 JBoss Drools Core Development
 JBoss by Red Hat @ www.jboss.com
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