Databases Reference
In-Depth Information
Temporal Insert
Physical Transaction(s)
Insert an object into a
designated timespan.
Assert a version.
Reset affected versions.
Figure 10.1 The Temporal Insert Transaction: Temporal to Physical Mapping.
The end result, if successful, is that the transaction has
an oid, an effective time period, and an assertion time period.
The default effective time period for a temporal transaction is
[Now() - 12/31/9999], but either effective date can be overridden.
The default assertion time period is also [Now() - 12/31/9999].
In Chapter 12, we will see what happens if the assertion begin
date default is overridden; but until then, we will assume that all
transactions accept this default.
The temporal insert is the simplest of the three temporal
transactions to implement. There are no existing versions to
be withdrawn and then replaced and/or superceded. As long
as not a single clock tick in the transaction's target timespan
[
intersects]
the effective time period of some version of the
same object that is already in the target table, the insert is valid.
Otherwise, the transaction would violate TEI, and therefore is
rejected by the AVF.
A valid insert is always carried out by creating one version.
Sometimes the result is a new episode. Sometimes the result is
to {lengthen an existing episode forwards}.
1
Sometimes, in being
lengthened, an episode “bumps into” another episode and the
two episodes are {merged}. When an insert creates a new epi-
sode, or {lengthens an episode forwards} (without bumping into
the next episode), no other versions are affected. But otherwise,
i.e. when {lengthening an episode backwards} or when {merging}
two episodes, an insert does require some adjustment on the
part of other versions.
1
“{lengthen forwards}” is a two-word temporal extent state transformation name that,
for the sake of readability, often needs a pronoun or a noun in the middle. For
example, “{lengthen it forwards}” or “{lengthen an episode forwards}”. In any of these
alternative forms, however, it is still the {lengthen forwards} transformation that is
being referred to. The same is true for the names “{lengthen backwards}”, “{shorten
forwards}” and “{shorten backwards}”.
