SemanticJsonExport is a mediawiki extension to allow export semantic data of pages
place extension in the 'extensions' directory of your mediawiki, in a folder Called "SemanticJsonExport" and add this to your localsettings.php file :
wfLoadExtension('SemanticJsonExport');
got go tpage Spécial:ExportSemanticJson and enter the pages you want to export
this extension add a hook :
'SemanticJsonExportBeforeSerializePage' [ Title $title, &$data ]