XML.com FAQs > C. Authors of SGML (including writers of HTML: Web page owners)
Question:  C.19 Can I use Java, ActiveX, etc in XML files?

This will depend on what facilities the browser makers implement. XML is about describing information; scripting languages and languages for embedded functionality are software which enables the information to be manipulated at the user's end, so these languages do not have any place in an XML file, but in stylesheets like XSL and CSS.

XML itself provides a way to define the markup needed to implement scripting languages: as a neutral standard it neither encourages not discourages their use, and does not favour one language over another, so the field is wide open.

This FAQ is from The XML FAQ, maintained by Peter Flynn