What is exact implementation of Model data (or Graph) in Apache Jena?

Question

I understand Model like this :
It consists of triplets ( Subject Predicate/Property Object)

A B C
C D E
E F G
G H I
X Y Z

And We can represent above set of Triplets with Nodes and Edges in Graph.
I want to get Subject 'A' value which can have chaining like above C->E->G->I in Model and in terms of Graph It should return SubGraph from 'C' node.

Here is my Recursive code:

 public Model getRecursive(String subject) {
    Model newModel = ModelFactory.createDefaultModel();

    StmtIterator it = this.model.listStatements();
    while (it.hasNext()) {
        Statement statement = it.next();
        if(statement.getSubject().toString().equals(subject))
        {
            newModel = newModel.add(statement);
        }
    }

    Model objectModel = ModelFactory.createDefaultModel();
    it = newModel.listStatements();

    while (it.hasNext()) {
        Statement statement = it.next();
        objectModel = objectModel.add(getRecursive(statement.getObject().toString()));
    }

    newModel = newModel.add(objectModel);

    return newModel;
}

But my problem is its complexity is too high.
Assume Model have 1000 triplets and a Subject assume 'A' have chain length of 10.Then According to my code , time complexity is 10*1000 because my recursive code for each call iterate through whole triplets to find triplets with current given Subject and then further recursively call on Object values.

Is there any other way to do it fastly ? I didn't get any methods in graph and Model which can do it fastly .

Answer 1

Jena models are indexed - you don't have to scan them to find things.

First, work with resources, not strings:

Resource subject = model.getResource(uristring) ;

and then pass in an accumulator:

Model acc = ModelFactory.createDefaultModel();

so as not to copy results all the time.

recurse(Resource start, Model acc) ;

To access the model, use listStatements(s,p,o), which takes arguments as to what you are looking for.

StmtIterator sIter = model.listStatements(subject, null, (RDFNode)null) ;

finds statement with that subject only.

which is packaged up as as method on resource:

StmtIterator sIter = subject.listProperties() ;

(subject knows which model it is in).

In addition, you should check for cycles or it will recurse forever.