TEMPORAL DATABASE CONCEPTS

TIME REPRESENTATION

§  Time is considered to be an ordered sequence of points in some granularity that is determined by the application.

§   Chronon. A chronon is the shortest duration of time supported by a temporal DBMS.

§     It is a non-decomposable unit of time.

§  Point events

–        Single time point event

l  E.g., bank deposit

–        Series of point events can form a time series data

§  Duration events

–        Associated with specific time period

l  Time period is represented by start time and end time

CALENDARS

§  A calendar organizes time into different time units for convenience.

§  Most calendars group 60 seconds into a minute, 60 minutes into an hour, 24 hours into a day Accommodates various calendars

§  Gregorian (western)

§  Chinese

§  Islamic

§  Hindu

TIME DIMENSIONS

§  Valid Time

               Time that the event occurred, or the period during which the fact was   considered to be true in the real world.

§  Transaction Time

       Time when the information was actually stored in the database

§  Bitemporal database

–        Databases dealing with two time dimensions