Update July 16: Please see InstallAll instead

How to

... assuming that you have a working Semantic MediaWiki installation (Tested with MW 1.15 and later)

• Download the ARC2 library from here
• Extract and place it in wiki/extensions/SemanticMediaWiki/libs/arc, so that the file ARC2.php is placed in the arc folder
• Download all the files in https://code.google.com/p/smwrdfio/source/browse/#svn/trunk ...
• ... and place them in wiki/extensions/RDFIO/, if "wiki" is your MediaWiki installation folder
• Add the following to your LocalSettings.php:

/**************************
 *  ARC2 RDF API for PHP  *
 **************************/

$smwgARC2Path = $smwgIP . '/libs/arc/';
require_once($smwgARC2Path . '/ARC2.php');

/**************************
 *  ARC2 RDF Store config *
 **************************/

$smwgARC2StoreConfig = array(
              /* Customize these details if you   *
               * want to use an external database */
		'db_host' => $wgDBserver,
  		'db_name' => $wgDBname,
  		'db_user' => $wgDBuser,
  		'db_pwd' =>  $wgDBpassword,
		'store_name' => 'arc2store',
);
$smwgDefaultStore = 'SMWARC2Store'; // Determines database table prefix

require_once("$IP/extensions/RDFIO/SMW_ARC2Store.php");
require_once("$IP/extensions/RDFIO/SpecialARC2Admin.php");

• Log in to your wiki as a super user
• Browse to http://[your-domain]/wiki/Special:ARC2Admin
• Click "Setup" to create database tables for the ARC2 RDF store
• Try adding some semantic data to wiki pages, and then check the database (using phpMyAdmin e.g.) to see if you get some triples in the table named arc2store_triple