The widespread use of XML brings out the need of ensuring the validity of XML data. The use of languages such as XML Schema makes easier the process of verification of XML documents, but the problem is that there are many constraints that can not be expressed by means of XML Schema. Besides, several works in the literature defend the consideration of a conceptual level in order to save XML designers from dealing with low level implementation issues. The approach of this paper is based on the inclusion of such a conceptual level, using UML as a conceptual modeling language. Starting from a UML class diagram annotated with conceptual constraints, our framework automatically generates an XML Schema together with a set of XSLT stylesheets to check those integrity constraints that can not be expressed in XML Schema.