Split and re-serialize graph (RSS)

[Dan Libby]

Hi, I am trying to use RAP to parse and re-serialize some custom RSS 1.0 feeds (ie, with some custom namespaces.)

I assume that each RSS file may have N number of channels within it, and each channel N number of related items.  Each of these channels and its items should be unrelated to the other channels.

I would like to grab all the triples for a given channel and its elements and put them into a new model for serialization.  Thus effectively splitting the multi-channel file into several single channel files. ( or even handier would be a "serialize graph from this node" function. )

I know how to grab the relevant channel resources.  And I know that  I can recursively forward walk the graph starting from the channel.  However, I am concerned about endless loops if someone feeds me some bogus RDF.  I guess I would have to keep a list of "already seen" nodes.

So then for each statement that I find during the walk I would add it to a new model.  When finished walking, I serialize this new model, and voila, a file specific to this channel.

Can anyone comment on the validity and efficiency of this approach or recommend something better?  I'd rather not re-einvent the wheel. Does code for this already exist somewhere?

regards,

Dan Libby

[Dan Libby]

In case it is useful to someone else, I have come up with the following code that seemsto do the trick.

   function copy_node_to_model( &$model, $resource ) {
   
      $seen_list = array();
     
      copy_node_to_model_worker( $model, $resource, $seen_list );
     
      $resource->setAssociatedModel( $model );
     
      return $resource;
    }
   
    function copy_node_to_model_worker( &$model, $resource, &$seen_list ) {
   
       $uri = $resource->getURI();
       if( !isset( $seen_list[$uri] ) ) {
      
          $seen_list[$uri] = 1;
      
          $statements = $resource->listProperties();
          foreach( $statements as $s ) {

             // Duplicate the statement, but we change the model for the sub, pred, and obj.
         
             $sub = $s->getSubject();
             $pred = $s->getPredicate();
             $obj = $s->getObject();
            
             $sub->model =& $model;
             $pred->model =& $model;
             $obj->model =& $model ;
         
             $model->addWithoutDuplicates( new Statement( $sub, $pred, $obj ) );
            
             $obj = $s->getObject();
             if( is_a( $obj, 'Resource' ) ) {
                copy_node_to_model_worker( $model, $obj, $seen_list );
             }
          }
       }
    }