3.1 Required Articles
A specification book and each of its chapters carry a fixed opening and closing shape, so that a reader arriving at any chapter finds the same things in the same places.
3.1.1 Book level #
A book MUST open with an introduction chapter containing:
| Article | Purpose |
|---|---|
| Scope | What the book covers, and what it does not — with each exclusion naming where the excluded thing is covered |
| Conventions | The book's RFC 2119 declaration and any notation specific to it (§3.3) |
3.1.2 Chapter level #
A chapter specifying a protocol or a format MUST open with:
| Article | Purpose |
|---|---|
| Scope and Roles | What the chapter specifies, and the roles that speak it (§3.2) |
| Terminology | Terms specific to the chapter |
and SHOULD close with an Extension article (§3.4) and a Conformance article (§3.4), in that order, before any appendices.
A chapter defining a data structure rather than a protocol has no roles and no conformance obligations of its own, and is exempt from both.
3.1.3 Terminology delegates rather than repeats #
A terminology article MUST define the terms the chapter introduces. A term already defined elsewhere in the corpus MUST be delegated by reference rather than redefined:
3.1.4 Scope names its exclusions #
A scope article's exclusion list MUST identify, for each excluded item, which document covers it. An exclusion that names nothing tells a reader the subject is out of scope without telling them where to go, which is the least useful thing a scope article can do.