Platform Release 12 included a very useful new feature: the ability to send more than one changeset in a single POST to your store.

To generate a batch changeset from 2 versions of an RDF graph, you can use an ARC plugin called Talis_ChangeSetBuilderPlugin.

To use it:

	  $args = array(
			'before' => $before, //can be rdf/xml, turtle, or an ARC simpleIndex array
			'after' => $after,  //can be rdf/xml, turtle, or an ARC simpleIndex array
		);
		$cs = ARC2::getComponent('Talis_ChangeSetBuilderPlugin', $args);
		$cs_response = $store->get_metabox()->apply_versioned_changeset($cs); 

The plugin also relies upon the IndexUtils Plugin. The easiest way to get them all set up is to change to your arc directory and do:

svn co http://n2.talis.com/svn/playground/kwijibo/PHP/arc/plugins/trunk/ plugins

A common trouble when parsing RDF is running out of memory because the document is too large. ARC2 solves this problem (for RDF/XML) by being able to stream it.

If you want to take advantage of the streaming, you just need to extend the ARC2_RDFXMLParser class and overwrite the addT method:

<?php
require 'arc/ARC2.php';
require 'arc/parsers/ARC2_RDFXMLParser.php'; 

class Streamer extends ARC2_RDFXMLParser { 

	function addT($s, $p, $o, $s_type, $o_type, $o_dt = '', $o_lang = ''){
		var_dump($s, $p, $o, $s_type, $o_type, $o_dt, $o_lang);
	} 

} 

$p = new Streamer(); 

$p->parse('big-data.rdf'); 

?>

In this simple example, I’m just var_dumping out the triples as they come in, but of course you should do whatever it is you want to do instead to the triple in that method.