What is the process for defining new metadata semantics?

[lilleyse]

The 3D Metadata Specification allows a property to be assigned a semantic, which indicates how the property should be interpreted.

The semantic may be one of the common semantics defined in the 3D Metadata Semantic Reference (e.g. NAME or ID) or a semantic defined in some other semantic specification. The current approach is intentionally very minimal and open-ended since community feedback may bring us in new directions like XMP-style namespaces (CC https://github.com/CesiumGS/3d-tiles/issues/554) or semantics at the schema or class level.

Some of the open questions are:

• How are new common semantics added to the 3D Metadata Semantic Reference?
• How are domain- or application-specific semantic dictionaries defined?
• Does the addition of a new semantic require a new extension or can the semantic be defined in some standalone way? #127

Examples of semantics that could be defined:

• https://github.com/CesiumGS/3d-tiles/issues/176#issuecomment-969141863
• https://github.com/CesiumGS/3d-tiles/issues/287
• https://github.com/CesiumGS/3d-tiles/issues/99