A shape refines another declaration of its lane; four ids are reserved
The rule
Normative: this is the rule
- Where two sources declare the same lane id, the site's own declaration wins over a code-declared shape, and both win over the shipped entry.
- The winner replaces the entry whole rather than key by key, because a partial shape is a deliberate redefinition.
- A collision with a shipped id is therefore not a break: the lane stays in the vocabulary, stays self-compatible, and keeps its derived rules.
- Precedence is resolved in one place, so which declaration wins never depends on load order.
- The ids
trigger,tool,mixedandanyare reserved (every generated compatibility rule in the payload is built from them), and a shape naming one is ignored rather than fatal, since paths that reach around a form exist and one bad shape must not unwire every canvas.
Rule identifiers are permanent and are never renumbered. Each implementation publishes its own standing against these rules; this specification does not.spec 1.0-draft · SCH-44 · changed in spec 1.0