I have a question regarding creating a list of items that are all in nested collections of my main object.

A high level overview of the model is like this:

public Level0 {
 private List<Level1> level1List;
}

public Level1 {
 private List<Level2> level1List;
}

public Level2 {
 private Date occurence;
}

Now, I add objects of type 0 in the working memory and for each of those objects, I want to find the latest occurrence of a certain Level2, regardless of which level1 they belong to.

If there’s only 2 levels and I want to find the latest occurrence of Level2’s with a certain name, I can write:

rule "latest level 1"

when

$l0: Level0()

$date: Date() from accumulate (Level1(name in ("name1", "name2"), $occurence: occurence) from $l0.level1List, maxDate($occurence))

then

// register fact that latest occurrence of name1/name2 level1 was on $date

end

Now, with 3 levels, since I obviously can’t replace $l0.level1List with $l0.level1List.level2List, is there a way to create an intermediate list that will contain all Level2 objects? No filtering needs to take place on Level1, but if there’s a way to do that too, that would be nice.

What I currently have is this:

rule "latest level 2"

when

$l0: Level0()

$l1: Level1() from $l1.level1List

$l2List: List(size > 0) from collect( Level2(name in (("name1", "name2")) from $l1.level2List )

$date: PartialDate() from accumulate (Level2( $occurence: occurence) from $l2List, maxDate($occurence))

then

// register fact that latest occurrence of name1/name2 level2 was on $date

end

But this does not work as it treats each Level1 seperately: it creates a “latest occurrence” for all accumulated level2 facts within a level1, instead of one for the entire set of level 2’s ‘owned’ by the level0 object.

Any suggestions?