Simple SPARQL example.

The following example shows the code needed for a simple example:

`1. Include XaLib in your XUL file.`

`2. Include the Query Engine in your Javascript code.`


XaLib.include("chrome://xalib/content/RDF/SPARQL/Query.js");

`3 Declare variables used in the query:`

var _subject = new Var("Subject");

var _predicate = new Var("Predicate");

var _object = new Var("Object");

`4. Construct the query using a Javascript object literal:`

Query Literal syntax details can be found here.


var q;

eval (

    q = new Query({

    

        // The
Prefix clause defines a
set of namespace prefixes used to shorten the form of RDF resources.
  

        Prefix:
{ext:"http://www.mozilla.org/2004/em-rdf#"},

        

        // The
Select clause indicates
the variables to be included in the results.  

        Select:
[_subject, _predicate,
_object],

        

        // The
From clause gives a list
of RDF files to be queried.

        // The dir: protocol is an
XaLib way to
access well know directories.   

        From:
["dir://profile/extensions/extensions.rdf"],



       
// The Where clause
specifies which data is to be returned by the query.

        Where: [ 

       
Triple(_subject, _predicate,
_object)

       
]   

    });

);

`5. Execute the query.`


q.compile();

q.execute();

`6 Iterate through the results:`


var itr = q.results();

var result;

// (The double parentheses stop
strict mode warnings.)

while ((result = itr() )) {

    // The result property names relate to
the names
passed to the Var constructors above.

    alert("Subject:" + result.Subject + " Pedicate:" +
result.Predicate + " Object:" + 
result.Object);

}