Versioning and Extensions

The optional workfile key declares the major format version that a file targets. Within a major version, this standard adds only optional keys.

An unknown key is an error, not a warning.

Vendor-specific keys. A vendor-specific key MUST use the x- prefix. Implementations MUST accept a key whose name begins with x- in any map of a Workfile, a manifest, or an overlay. Implementations MUST ignore such a key when they evaluate the document, and MUST NOT let it alter the meaning of any construct. A resolved definition MUST preserve x- keys, so that a tool can read them after resolution.

Closed vocabularies. The expression grammar, the core filter set, the error vocabulary, the type system, the capability names, and the reserved namespaces are closed within a spec version. The registries state how each is amended.

A reserved namespace MAY gain a canonical manifest within a major version. A reserved namespace MUST NOT be reassigned.

Errata. A defect in this specification is corrected by an erratum against a spec version, or by a later spec version. The conformance suite is amended together with the prose. A correction MUST NOT change the meaning of a construct within a major version, except to resolve a contradiction.