[rules-users] Noob question: graph searching, query, root node for a given node

[Mark Proctor]

> I want a query that takes a datum and yields the root nodes for that datum.
Do you mean root node or nodes? Surely there can only be one root? Or do you mean you are looking for the leafs?

Mark
On 18 Jun 2014, at 13:31, Borris <borris at chaos.org.uk> wrote:

> I'm after a quick bit of help on how to do something that I think should be
> easy but I can't work out how.
> 
> I have a Java-side class that essentially is something like
> 
> declare Datum
>    description: String
>    broader: List <Datum>
>    narrower: List <Datum>
> end
> 
> These are arranged in a graph. Root nodes have no items in their broader
> list. I want a query that takes a datum and yields the root nodes for that
> datum. I think this should look something like
> 
> query rootDatumsFor( Datum datum, Datum result )
>    not Datum() from $datum.broader
>    or
>    rootDatumsFor( $datum.broader, $result )
> end
> 
> but I then get confused. When there are no broader items, I am unclear how
> to assign $datum to $result. And I'm not convinced I'm doing the recursion
> correctly either.
> 
> If an experienced Drools author could spend a minute and show me how to do
> this sensibly, I would be very grateful.
> 
> 
> 
> 
> 
> 
> --
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