Metadata

ProvenDB adds metadata to each document which includes a hash value and effective version numbers. Normally, this metadata is suppressed. However, the showMetadata command can be used to request that metadata be displayed in query results. This command takes effect across all sessions for a given user.

ProvenDB maintains a set of collections that are used to define version information and record proofs. These collections cannot be modified by ProvenDB users but can be viewed normally. The diagram below documents these collections.

User collection metadata

The attributes added to each user collection in the _provendb_metadata embedded document are listed below

Attribute	Description
hash	Hash value for the document. The hash includes metadata attributes but (of course) not the hash itself
minVersion	The database version in which this version of the document first became visible
maxVersion	The database version in which this version of the document last became visible
forgotten	If true, the contents of this document have been forgotten
_id	the "ProvenDB" _id - this is the same for all versions of a document
mongoId	The actual MongoDB "_id" of the document. Unlike the provenDB _id , this value changes every time a document is updated.

provenDB metadata collections

Below is a definition of each ProvenDB metadata collection

Name	Description
_provendb_versions	Contains details of each database version including it's timestamp and status
_provendb_versionProofs	Contains details of each proof created in the database including it's Chainpoint proof, collections included in the proof and bitcoin block and tranaction ids
_provendb_collections	Contains collection-level locking information.
_provendb_currentVersion	Contains a single document that defines the current version status
_provendb_forgetRequests	Records the status of each forget request.
_provendb_documentProofs	Contains details of document proofs that have been requested. This acts mainly as a cache to avoid recalculation of document proofs should the same document proof be requested more than once