-----------------
rule "Total Costs"
when
$person : Person( eval ($person.maxMoney != null ) )

Although not relevant to your problem: stick with the JavaBean convention: There should be private Integer maxMoney; Integer getMaxMoney(); etc. and then you write
Person( maxMoney != null )

$totalCost : Number()
                from accumulate(    $trip : Trip( $cost : $trip.getCost() ) from $person.getTrips(),

                                           sum( $cost )
                                      )

Again: Trip should have private Integer cost; Integer getCost() etc. and then you
do
    Trip( $cost: cost ) ...

To call an arbitrary method you should be able to do
   sum( $trip.getCost() )

All together:
$person: Person( $maxMoney: maxMoney != null, $trips: trips != null )
Number( $spent: intValue > $maxMoney )
    from accumulate( Trip( $cost: cost ) from $trips, sum( $cost ) )

-W

then
     // take action
end

-------------------

I have tried it with and without the $trip-variable (since I thought I might have to use it to call its function).

The error I get looks like this:

Error INTERNAL_ERROR: Error: unknown:70:54 Unexpected token ')'

java.lang.Exception: Error: unknown:70:54 Unexpected token ')'
        at com.fluidops.coremgmt.ruleengine.PolicyTask.readRule(PolicyTask.java:489)

        at com.fluidops.coremgmt.ruleengine.PolicyTask.readRule(PolicyTask.java:419)

I would be very thankful if one of you could help me out here :)

Best regards,
Christian

PS: I already had this question in the drools forum, it was, however not forwarded to this mailing list, so please forgive me if it is a double post.

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