[Rdfapi-php-interest] Bug in reification code (and fix)

[Richard C. <ri...@cy...>]

Hi,

There's a bug in Statement::reify.

According to the Statement documentation, you can pass a blank node  
to the function. Test script:

    <?php
    define("RDFAPI_INCLUDE_DIR", "./rdfapi-php/api/");
    include(RDFAPI_INCLUDE_DIR . "RdfAPI.php");
    $a = new Resource("http://example.org/a");
    $b = new Resource("http://example.org/b");
    $c = new Resource("http://example.org/c");
    $statement = new Statement($a, $b, $c);
    $model = ModelFactory::getDefaultModel();
    $blank = new BlankNode($model);
    $reification_quad = $statement->reify($blank);
    echo $reification_quad->writeRdfToString();
    ?>

This throws a bunch of warnings and then produces this output:

<rdf:RDF
    (snip namespaces)
<rdf:Statement rdf:nodeID="Object">
    <rdf:subject rdf:resource="http://example.org/a"/>
    <rdf:predicate rdf:resource="http://example.org/b"/>
    <rdf:object rdf:resource="http://example.org/c"/>
</rdf:Statement>

Note the rdf:nodeID="Object". It should say something like bNode1.

The fix is easy. Quote from the body of Statement::reify:

   function & reify(&$model_or_bNodeID) {

         if (is_a($model_or_bNodeID, 'MemModel')) {
             // parameter is model
             $statementModel = new MemModel($model_or_bNodeID- 
 >getBaseURI());
             $thisStatement = new BlankNode($model_or_bNodeID);
         } else {
             // parameter is bNodeID
             $statementModel = new MemModel();
             $thisStatement = new BlankNode($model_or_bNodeID);
         }

Note the last line: $model_or_bNodeID contains a blank node, but we  
create a new blank node anyway, with the blank node as argument!

The line should read:

             $thisStatement = &$model_or_bNodeID;

(It's line 271 of /api/model/Statement.php)

Related issue: I don't see a reason why the method is restricted to  
blank node arguments. Passing a URI should also be allowed. There's  
actually nothing in the code to make it specific to blank nodes.  
Passing a URI should work just fine. I suggest the method  
documentation and variable names be updated to also allow blank nodes.

Cheers,
Richard