One of the most common uses (read: abuses) of server-side scripts is to perform the simple task
of merging two HTML documents: typically a template including navigation, plus the page
content. Others use programs like Dreamweaver to accomplish the same goal on the author's
side.

The Embedding Attributes Module[1] briefly mentions the media type "application/xml" - is it
anticipated that user agents would allow XHTML 2.0 documents to embed other XHTML 2.0
documents? Extra navigation (i.e., a sidebar in conventional screen presentation) could be
embedded this way, instead of relying on PHP, ASP, etc.

- Ed.

[1] http://www.w3.org/TR/xhtml2/mod-embedding.html#s_embeddingmodule