It is now straightforward to develop a range of different stylesheets to present XML documents in different ways, for example to create personalised presentations. If the XML document is available on the World Wide Web, then (subject to copyright) anyone can create their own stylesheet to present that document in new ways. This has the potential to allow improved “added value” services, such as personalised news feeders. But the power of stylesheet languages such as XSLT means that the document may be substantially transformed, with sections deleted or re-ordered. This re-structuring may result in a misleading and even dangerous presentation. This paper presents some proposals for putting some control in the hands of document authors, to allow them to indicate allowable transformations, and to provide a limited validation mechanism to verify that a transformed document meets the requirements of the author.