Custom annotation for dispensable properties

[mih]

Example: a publication is defined by a DOI. A schema would nevertheless support specification of other properties to also support publication that do not have a doi. Now a record might have a DOI and those additional properties, and they may conflict (e.g. journal from doi inference vs journal property).

It would be good to declare some kind of level-of-essentialness for properties within the schema, to indicate preferences.

Also, it would be good to outline provenance of metadata (yes, of), to be able to tell whether metadata. ame from a manual annotation, or an automated query, or was manually verified, etc.)