Separation of Content from ...

The document "Architecture of the World Wide Web, Volume One"
(http://www.w3.org/2001/tag/webarch/) says, "A specification SHOULD
allow authors to separate content from both presentation and interaction
concerns."   I wonder if it would be possible and useful to extend that
at bit.  It seems to me that there are other classes of purposes for
which statements might be mixed in with content.  In particular, one
could have statements that define:
1 - presentation
2 - interaction
3 - data transformation
4 - data semantics
Would it be architecturally desirable to separate all five of these
things?
To try to avoid being disingenuous, I might remark that this thought
came to me after hearing a presentation at WWW2006 describing an XML
processing scheme that mixes transformation (processing) statements in
with the XML data.  This struck me intuitively as a "bad idea" from an
architectural viewpoint, however useful it might be for some purposes.
Of course, I am far from confident that I am correct in this reaction,
but it seems to me that the issue might merit a bit of discussion.
Apologies if this issue has already been discussed elsewhere.