[rules-users] About fusion and collections

[Edson Tirelli]

   Amit,

   Check fireUntilHalt() docs in order to set the engine to reactive mode...
although, for most cases I've seen, you still have more control by defining
the fireAllRules() cycle explicitly.

   Regarding your rule, the problem is that the first type is matched for
multiple events. The simplest way to fix that is by pre-populating the
working memory with all possible event types. In this case you would use a
rule like:

when
    EventType( $type : type )
    $events: ArrayList (size > 10)
            from collect (Event(eventType == $type))
then
    // do something
end

   You can also find the distinct event types using accumulate, but that is
heavier and more complex than the previous example. Lets say event type is a
String:

when
    $types : Set()
         from accumulate( Event($type : eventType),
                                   collectSet( $type ) )
    $type : String() from $types
    $events: ArrayList (size > 10)
            from collect (Event(eventType == $type))
then
    // do something
end

   I don't really recommend the second approach though. An intermediate
approach is to have a separate rule logically insert all event types, and
then use the same approach of the first example above:

declare EventType
    type : String @key
end

when
    Event( $type : eventType )
then
    EventType et = new EventType();
    et.setType( $type );
    logicalInsert( et );
end

   []s
   Edson


2010/3/15 Amit Kumar <amitkumar at gmail.com>

> Hello All,
>
> Was doing some rule writing and am seeing some issues which I want to
> overcome.
>
> In Fusion when we send the facts into working memory.. there seems to be no
> way that rules are automatically getting triggered.
> We have to call fireAllRules after each fact insertion. Is this the way it
> was designed. Its like this in the stocktick example also
>
> This one should be simple for somebody with little more experience than me
> In the following rule
>
> rule "raise alarm"
> when
>   Event($type : eventType)
>   $events: ArrayList (size > 10)
>             from collect (Event(eventType == $type))
> then
>   raise alarm
>
> In the above rule the raise alarm is getting called 10 times. .. How can I
> make it to be called only once.
>
> Thanks
> Amit
>
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>


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