35 ;;Quote: databases may model reality but they ignore time-varying aspects, e.g. historical queries and trend analysis

36 ;;Quote: conventional databases are a snapshot of the current state; may be somewhat out-of-date

36 ;;Quote: conventional databases can not handle historical queries, trend analysis, retroactive changes, or proactive changes

36 ;;Quote: a rollback database contains immutable snapshots indexed by time; can rollback the database to some time

37 ;;Quote: a historical database records a single historical state per relation; supports valid time, i.e. current knowledge about the past

37 ;;Quote: a temporal database can view tuples as seen from some time; captures history of retroactive/proactive change; sequence of historical states

37 ;;Quote: user-defined time, e.g., the date when the promotion committee approved the promotion