Terminology

PSD (Peios Specification Document): A formally numbered specification in the Peios spec corpus. Each PSD has a permanent numeric identifier and one or more versioned editions.

PSD number: A sequential positive integer permanently assigned to a specification. Format in prose: PSD-NNN (zero-padded to three digits). PSD numbers identify specifications, not versions.

Version: A specific edition of a PSD, identified by a SemVer string synchronised with the Peios software release it ships with. Versions are sparse -- a PSD may jump from v0.22 to v0.56.1.

Revision: The count of how many versions a PSD has had. Derived from the number of version directories. Not stored explicitly.

Chapter: A top-level section of a PSD, corresponding to a numbered directory within the version directory. Example: 3-security-descriptors/ is chapter 3.

Section: A file within a chapter directory. Example: 2-acls.md within chapter 3 is section 3.2.

Subsection: A markdown heading within a section file. ## headings are subsections; ### headings are sub-subsections. Depth is unlimited.

Clause: A specific normative statement within a section or subsection. Clause numbers are positional -- derived by counting normative statements sequentially within the most specific section. Cited in parentheses: (1), (2).

Normative: Text that defines required, prohibited, or permitted behavior. All text in a PSD is normative unless explicitly marked otherwise.

Informative: Text that provides explanation, context, or examples but does not define behavior. Marked with > [!INFORMATIVE] block quotes or introduced with "For example" or "Note:".

Version resolution: The rule by which a PSD reference without an explicit version is resolved: the highest version of the referenced PSD whose version number is less than or equal to the version of the referencing document.

Trail: The Peios static site generator that renders PSDs. Trail is the primary publication tool but PSDs are designed to be readable and navigable without it.