Databases Reference
In-Depth Information
physical logfile
Mechanics:
the ability of the AVF to recreate the state of an asserted version table
as of any past point in time, using the row create date.
Comments:
See also
semantic logfile
.
Deferred assertions which have been retrograde moved from far future to
near future assertion time are the one exception to this ability to recreate
any past physical state of an asserted version table. Currently, Asserted
Versioning does not preserve information about the far future assertion
time these assertions originally existed in. (From Chapter 16.)
Components:
asserted version table, AVF, row create date.
physical transaction
Description:
a SQL insert, update or delete transaction submitted to the DBMS.
Comments:
The AVF translates each temporal transaction into the one or more
physical transactions that, when processed, carry out the intentions
expressed by the user who submitted the temporal transaction.
pipeline dataset
Mechanics:
a dataset whose destination or origin is one or more production
tables.
Comments:
Pipeline production datasets (
pipeline datasets
, for short) are points at
which data comes to rest along the inflow pipelines whose termination
points are production tables, or along the outflow pipelines whose points
of origin are those same tables. (From Chapter 12.)
Components:
dataset, production table.
pipeline dataset, internalization of
Mechanics:
the representation of the contents of external pipeline datasets as
rows in asserted version production tables which exist in non-current
assertion time and/or non-current effective time.
Components:
asserted version table, assertion time, current assertion, current
version, effective time, external pipeline dataset, production table, represent.
pipeline dataset, re-presentation of
Mechanics:
the ability to recreate the contents of any external pipeline dataset
from internal pipeline datasets by means of a query.
Components:
external pipeline dataset, internalized pipeline dataset.
point in time
Mechanics:
a time period whose begin date value, using the closed-open
representation of time periods, is one clock tick before its end date value.
Semantics:
a time period consisting of a single clock tick.
Comments:
For purposes of temporal data management, a point in time is considered
indivisible.
Note that in this topic, in which we use a month as our level of temporal
granularity, that one month is considered indivisible. For example, if a
transaction is applied, it is assumed that its results will remain
unchanged until the next month.
Components:
begin date, clock tick, closed-open, end date, time period.
