Revisions:

Record contains representations ------------->representation has versions ------------> versions contains files and has revisions ----------------------> revision is marked by tags.

Versions may have revisions. One or more revisions of a version can exist and they may be used to governs necessary workflows and filter their queries. Each revision is uniquely identified by three parts: revision_name , revision_provider and revision_timestamp.

Tags are proposed to mark/tag a revision with a specific state. To be more specific, Tags are a set of three boolean flags(accepted, published and mark_deleted) which could be used as a filtering criteria.