ZNF framework Setup Not Run.

I am trying to install the ZNF PEAR modules in my server but in the file Translation.php
happens a error , to refer at following variables :
Code: ( php )
1.$translationDefaultXpath = new DOMXPath($translationDefaultXml);
2.$translationDefaultXpath->registerNamespace('tra','znf-translation');

The server returns following warning :
"PHP Warning: DOMDocument::schemaValidate()[<a href='function.DOMDocument-schemaValidate'>function.DOMDocument-schemaValidate</a>]: Element '{znf-translation}znf-translation': Missing child element(s). Expected is ( {znf-translation}item ). in /path/to/Translation.php on line 100 ".

Please, if you can to give me an idea what's happen.