[quote]
* "Something" - a resource, a non-virtual object

At any point in time I have a description of Something which has multiple representations in different mediatypes, all semantically matching or equivalent:

* "something.rdf" - representation of Something with mediatype RDF+XML
* "something.n3" - representation of Something with mediatype RDF+N3
* "something.en.html" - representation of Something, in english, with mediatype text/html
* "something.de.html" representation of Something, in german, with mediatype text/html
[/quote]

to

[modified]
* "Something" - a resource, a non-virtual object

At any point in time I have a description of Something which has multiple representations in different mediatypes, all semantically matching or equivalent:

* "something.rdf" - representation of a description of Something with mediatype RDF+XML
* "something.n3" - representation of a description of Something with mediatype RDF+N3
* "something.en.html" - representation of a description of Something, in english, with mediatype text/html
* "something.de.html" representation of a description of Something, in german, with mediatype text/html
[/modified]

because you are saying "I have a description of Something which has multiple representations"

I don't think there are any errors here, but I do have a couple suggestions:

* Keep in mind TBL's URI Axioms, especially...

Axiom: Opacity of URIsThe only thing you can use an identifier for is to refer to an object. When you are not dereferencing, you should not look at the contents of the URI string to gain other information.

* As a sanity-check, consider how one would configure Apache to implement these; see e.g. Apache's docs on Content Negotiation.

* I think you over-emphasize the "user" in User Agent, but keep in mind I've been yelling at people for talking about "clicking on DOIs" for fifteen years, too! But seriously, browsers are merely "machines" operating on the user's behalf, playing their role in the HTTP transaction based on (a) hard coding, (b) configuration and (c) user response. So I think less emphasis on human interaction, perhaps a single unified user agent section, would make the discussion less confusing ;)

John