thank you for your extension.
but when i clicked submit button but, there was no reaction, and "json.query is undefined" in web browser console.
i debugged in firefox debugger
finally i found what is bug.
in function loadSelection of ext.semanticOLAP.js file, var query has category:category:pagenmae ..
so there was no result in api.php request..
you should modify definition of getQuery function.
request += '[[Category:' + $(this).val() + ']]'; => request += '[[' + $(this).val() + ']]';
that is, remove Category in the string.
after that, it works well.