With the proliferation of XML as the lingua franca of internet information exchange, engineering XML documents and maintaining their databases becomes a major challenge. In this context, the use of XML Schema to constrain and validate XML document content is becoming a standard part of web information production. However, adoption of XML Schema poses new problems; specifically, the difficulty in understanding even a relatively small schema due to its textual nature and XML syntax. This problem can be addressed by use of a graphical modelling language such as UML to document XML Schema and conforming XML document structure. This paper discusses the issues involved in representing XML Schema using UML and presents a transformation approach which is both comprehensive and thorough.