Modelling Valid Time: An Efficient Representation

The bitemporal conceptual data model proposed for handling time within the framework of relational data model can be eflcctiuely represented using valid-time and transaction-time intervals as time-stamps on tuples. We observe that in many real-world applications, valid-time interval for a fact is not known completely while entering the fact in a temporal database. The model provides ‘open’ interval, from some valid time v to ‘forever’ for time-stamping such facts. However, updating temporal validity of such facts, which invariably will be required, is not handled eficiently by this representation. We propose an alternative representation which can reduce storage cost by upto 50% and which also results in less I/O during updates. We define the conventional and temporal algebra opemtions for this representation, and also add a few useful operators for processing open interwals. We propose extensions to temporal SQL to support open-ended valid time intervals. keywords Temporal database, Query processing