Reach the same object with a set of predicates in Sesame

Question

Assuming (s,p,o) and list, I would like to use Model structure in Sesame and check if it is possible to use subject s, list of predicates and reach o at the end.

for example we say that there is a path, if for (s,p,o) and {p1,p2,p3}, there exists the following triples : (s,p1,o1) , (o1,p2,o2), (o2,p3,o)

Is there any possibility in Sesame or Model structure?

score 2 · Accepted Answer · answered Jan 17 '16 at 01:47

Probably the easiest way to do this is by means of a SPARQL query.

The query would be using a property path expression to express this path. Since you want to know if there exists a path for a given starting point and ending point, I assume a "yes" or "no" answer is good enough. So we can do a boolean ASK query:

ASK WHERE { :s (:p1|:p2|:p3)+ :o . }

This will return true if a path of any length exists between :s and :o that consists of some combination of properties :p1, :p2, and :p3.

Since you can't execute a SPARQL query directly on a Model, you will need to create an in-memory Repository and add your Model to it before doing the query, like so:

Model model = ...; // your model

// create and initialize a temporary in-memory store
Repository rep = new SailRepository(new MemoryStore());
rep.initialize();

try (RepositoryConnection conn = rep.getConnection()) {
   // load the model into the repository
   conn.add(model);

  // execute the query
  String query = "ASK WHERE { :s (:p1|:p2|:p3)+ :o . }";
  boolean pathExists = conn.prepareBooleanQuery(query).evaluate();
}

Alternatively, you can implement the path traversal yourself by means of a simple recursive method.

Model model = ...; // your model

IRI start = ... ; // your start point :s
IRI end = ...; // your end point :o .
IRI p1 = ...;
IRI p2 =  ...;
IRI p3 = ... ;

boolean pathExists = pathExists(model, start, end, p1, p2, p3);

With the actual method being something like this:

boolean pathExists(Model m, IRI start, IRI end, IRI... properties) {
    for(IRI p: properties) {
        Model fromStart = m.filter(start, p, null);  
        if (fromStart.contains(start, p, end)) {
               return true;
        }
        else { 
            for (Value obj: fromStart.objects()) {
                if (obj instanceof Resource) {
                     if(pathExists(m, obj, end, properties)) {
                            return true;
                     }              
                }
            } 
        }
    }
    return false;
}

...you may need to extend that a little bit (with a list of visited intermediate nodes to avoid infinite loops), but it illustrates the basic principle I hope. In any case, using a SPARQL query is far easier.

Reach the same object with a set of predicates in Sesame

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