__AUTOIDENT - Member identification

The number is used for creating unique integer key for globally defined properties (e.g. extension properties). In order to keep stored extension properties independent on its name, the number is used to identify extension properties stored for any instance.

Extension properties might be defined in the dictionary (common) or in the database (particular). Extension properties in the dictionary are numbered beginning with 1 000 000 000. Lower numbers are reserved for extension properties defined in databases.