Databases Reference
In-Depth Information
A temporal update's target range may include part of an epi-
sode or version, an entire episode or version, multiple episodes
or versions, or any combination thereof. But a temporal update
never creates a new episode, and never adds to or subtracts from
the total count of clock ticks occupied by its referenced object.
We will need only a single example to illustrate the most
important variations of temporal updates. We begin with a sam-
ple database whose rows 1-6 represent the versions 3-8 shown
in
Figure 10.4
. This is the sample database shown in
Figure 10.9
.
Row 1 represents version 7, the currently asserted replacement
for version 1. Row 2 represents version 8, the currently asserted
replacement for version 2. Rows 3-6 represent versions 3-6.
We will show none of the past assertion history that led to this
database state, but only the six versions that are currently
asserted. But because this is a relatively complex transaction,
we will illustrate its progress one physical transaction at a time.
The mapping shown in
Figure 10.8
illustrates the steps the
AVF will go through to complete the temporal update.
Temporal Update
Physical Transaction(s)
Update an object
within a designated
timespan.
Withdraw the affected
versions.
Assert the before-update
replacements.
Assert the after-update
successors.
Figure 10.8 The Temporal Update Transaction: Temporal to Physical Mapping.
Jan12
UPDATE Policy [P861, , , $40] Jul 2010, Jul 2011
Jan
2010
Row
#
1
2
3
4
5
6
Jan
2011
Jan
2012
Jan
2013
Jan
2014
epis-
beg
oid
eff-beg
eff-end
asr-beg
asr-end
client
type
copay
row-crt
P861
Feb10
Apr10
Oct10
Feb10
9999
9999
9999
9999
9999
9999
Jan10
C882
C882
C882
C882
C882
C882
HMO
$15
Feb10
P861
P861
P861
P861
P861
Apr10
Mar10
Jan10
HMO
$20
Apr10
Apr11
Apr11
Jul11
Apr11
Apr11
Apr11
PPO
$20
Jul11
9999
Jul11
HMO
HMO
$15
Jul11
Aug11
Jan11
Jan10
Mar11
Jan11
$20
$20
Aug11
Feb10
Oct11
Jan10
PPO
Oct11
Figure 10.9 Updating a Policy: Before the Transaction.
