Assuming I'm reading the tags right, you mark this as a "defined term," but just drop the link to the definition. I don't feel like that helps, since you now have a dangling defined term.

@MikeBishop as I said in #311, this is the most minimal approach. To do more, I think we need to rename 4. Header and Trailer Fields to something like "Messages", and expand its introduction accordingly.

Any thoughts about that?

It seems like most of the content you'd want for defining a message is already there in 2.1:

Nevertheless, a common abstraction is that a message includes some form of envelope/framing, a potential set of named fields up front (a header section), a potential body, and a potential following set of named fields (a trailer section).

Rearranging text a little to put that definition (and make it a definition, rather than "a common abstraction") by the introduction of the term "message" seems like it would work without having to rearchitect Section 4.

@MikeBishop x:dfn denotes use of a defined term, not a primary definition.

@royfielding ?