>Is it possible to embed an XML Schema in an XML document similar to the way that an internal DTD subset is embedded?
Sure it is possible as the schema is likely to be some kind of xml document itself you've in mind. You can embed the schema document (less the prolog kind of construction) in a custom tag and let the schema containing a description of the page plus the description of the custom tag containing the said schema with any kind of contents (to make life easier, else you can tighten it to be of type of schema of the schema.) As to the use of it, it depends on the application.