DIAGRAMS AND OTHER NOTATIONS - Managing Time in Relational Databases - page 127

epis-
beg

Row
#
1

oid eff-beg eff-end asr-beg asr-end client type copay row-crt

P861
P861
P861

Jan10 Apr10 Jan10 9999

9999
9999

Jan10 C882

C882
C882

HMO $15 Jan10

2
3

Apr10 Jul10 Apr10 Jan10

Jan10

HMO $20 Apr10

Jul10 Oct10 Jul10 PPO $20 Jul10

Figure 6.4 A Sample Asserted Version Table.

While illustrations are essential to understanding the com-
plexities of bi-temporal data management, it will also be useful
to have a notation that we can embed in-line with the text. In
this notation, we will use capital letters to represent our sample
tables. So far we have concentrated on the Policy table, and we
will use “P” to represent it.
Almost always, what we will have to say involves rows and
transactions that all contain data about the same object. For
example, we will often be concerned with whether time periods
for rows representing the same policy do or do not [meet]. But
for the most part we will not be concerned with whether or not
time periods for rows representing different policies [meet]. So
the notation “P[X]” will indicate all rows in the Policy table that
represent policy X.
In the next several chapters, we will be primarily concerned
with the effective time periods of asserted version rows. So for
example, the notation P[P861[Jun12-Mar14]] stands for the row
(or possibly multiple rows) in the Policy table for the one or
more versions of P861 that are in effect from June 2012 to March
2014. With this notation, we could point out that there is exactly
one clock tick between P[P861[Jun12-Mar14]] and P[P861
[Apr14-9999]]. If we needed to include assertion time as well,
the notation would be, for example, P[P861[Jun12-Mar14]
[Jun12-9999]]. If we were concerned with assertion time but
not with effective time, we would refer to the row(s) P[P861[]
[Jun12-9999]].
An example of the notation describing a complete asserted
version row is:

P[P861[Jun12-Mar14][Jun12-9999][Jun12][C882, HMO, $15]
[Jun12]]

We will use abbreviated forms of the notation wherever possi-
ble. For one thing, we will seldom refer to the row creation date,
until Chapter 12, because until we discuss deferred assertions,
the row creation date will always be the same as the assertion
begin date. Also, the episode begin date is always identical to
the effective begin date of the first version of an episode, so we