Time and Time Again: Managing Time in Relational Databases, Part 9

Time and Time Again: Managing Time in Relational Databases, Part 9: Completing Version Pattern 5 – DMReview:

We noted in Part 8 that Version Pattern 5 is equivalent to Version Pattern 3, but with the single episode constraint {SC 3-4} removed. However, in that same installment, we also pointed out a difference in the first semantic constraint for each pattern. Constraint {SC 3-1} states that “if a version for an object is followed by another version for that same object, the end date of the former version must be one tick of the clock prior to the begin date for the latter version.” But for multi-episode objects, clearly, there may be any number of clock ticks between the logical delete version for one episode, and the initial version of the next episode. We accommodated this change by specifying that constraint {SC 5-1} has the same wording as {SC 3-1}, except for replacing “if a version for an object …” with “if a non-terminal version for an object …”