glTF core and extension registry model

Document status: reviewed. Canonical source.

Summary

glTF keeps a focused base format and grows through registered extensions. extensionsUsed and extensionsRequired let consumers distinguish optional data from capabilities required for correct loading/rendering. Prefix governance separates Khronos, multi-vendor and vendor namespaces.

NUIF relevance

Borrow explicit used/required capability declarations and staged extension governance. NUIF additionally needs a normative opaque-preservation rule so an editor can round-trip unknown payloads without understanding them.