The XML Schema language is becoming the preferred means of defining and validating highly structured XML instance documents. We have extended the conventional mutation method to be applicable for W3C XML Schemas. In this paper a technique for using mutation analysis to test the semantic correctness of W3C XML Schemas is presented. We introduce a mutation analysis model and a set of W3C XML Schema (XSD) mutation operators that can be used to detect faults involving name-spaces, user-defined types, and inheritance. Preliminary evaluation of our technique shows that it is effectiveness to test the semantics of W3C XML Schema documents.