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

[Mark Proctor]

It looks like your graph is not in the WM, so you can just iterate the references. Here is an example of how to do this. 

@Test
public void testGraphIterationToFindLeafs() {
    String drl = "import " + Datum.class.getCanonicalName() + ";\n" +
                 "import java.util.List;\n" +

                 "query findLeafs(Datum datum, List results)\n" +
                 "    ( eval( datum.getChildren().size() == 0 ) and \n" +
                 "      eval( results.add ( datum ) ) )\n" +
                 "    or \n" +
                 "    ( eval( datum.getChildren().size() != 0 ) and \n" +
                 "      child : Datum( ) from datum.children and\n" +
                 "      findLeafs( child, results; ) ) \n" +
                 "end\n";

    System.out.println( drl );

    KnowledgeBase knowledgeBase = loadKnowledgeBaseFromString( drl );
    StatefulKnowledgeSession ksession = knowledgeBase.newStatefulKnowledgeSession();
    List<Datum> list = new ArrayList<Datum>();

    Datum d1 = new Datum("d1");
    Datum d2 = new Datum("d2");
    Datum d3 = new Datum("d3");
    Datum d4 = new Datum("d4");
    Datum d5 = new Datum("d5");
    Datum d6 = new Datum("d6");
    Datum d7 = new Datum("d7");

    d1.getChildren().add( d2 );
    d1.getChildren().add( d3 );

    d3.getChildren().add( d4 );
    d3.getChildren().add( d5 ) ;
    d5.getChildren().add( d6 ) ;
    d6.getChildren().add( d7 ) ;

    ksession.getQueryResults("findLeafs", d1, list);

    System.out.println( list );

}

public static class Datum {
    private String description;
    private List<Datum> children;

    public Datum(String description) {
        this.description = description;
        children = new ArrayList<Datum>();
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public List<Datum> getChildren() {
        return children;
    }

    @Override
    public String toString() {
        return "Datum{" +
               "description='" + description + '\'' +
               '}';
    }
}

On 18 Jun 2014, at 18:44, Borris <borris at chaos.org.uk> wrote:

> Good question. I'm supporting a graph rather than a tree, so theoretically
> there could be more than one node that has no parents. But in my particular
> use case I am constraining the data so that there is never more than one
> root node.
> 
> So how to find the root node (singular) from an arbitrary node in the graph
> is my goal.
> 
> 
> 
> --
> View this message in context: http://drools.46999.n3.nabble.com/Noob-question-graph-searching-query-root-node-for-a-given-node-tp4030091p4030096.html
> Sent from the Drools: User forum mailing list archive at Nabble.com.
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