Databases Reference
In-Depth Information
maintain either conventional or uni-temporal versioned tables,
this kind of maintenance is impossible. A conventional table
has no way of recognizing effective time. And it is semantically
illegitimate to create past versions in uni-temporal version
tables.
Here's why. If a past version were created in a version table,
let's say one with an effective begin date of a week ago, it would
be a lie. For all that week, the database would have said that the
object represented by that version was not in effect during that
week. Then, after the transaction, the database would say that
the object
was
in effect during that same week. One or the other
of those claims must be false. In fact, the latter one is.
But in a chapter whose purpose is to introduce notation that
will be used in the rest of this topic, much of what we have just
said anticipates more detailed discussions that will occur later,
particularly in Part 3.
Glossary References
Glossary entries whose definitions form strong inter-
dependencies are grouped together in the following list. The
same glossary entries may be grouped together in different ways
at the end of different chapters, each grouping reflecting the
semantic perspective of each chapter. There will usually be sev-
eral other, and often many other, glossary entries that are not
included in the list, and we recommend that the Glossary be
consulted whenever an unfamiliar term is encountered.
12/31/9999
until further notice
asserted version table
Asserted Versioning Framework (AVF)
assertion begin date
assertion end date
assertion table
assertion time period
transaction time period
bi-temporal data
business data
business key
