Databases Reference
In-Depth Information
episode end date
Mechanics:
the effective end date of the latest version of an episode.
Semantics:
the date on which the episode ceases to be in effect.
Components:
effective end date, episode, version.
epistemological time
Semantics:
the epistemological time of a row in a bi-temporal table is the period
of time during which we claim that the statement made by that row is true
and/or actionable.
Comments:
A neutral term referring to either the standard temporal model's
transaction time or to Asserted Versioning's assertion time.
See also: “
assert” cognates
.
Components:
actionable, “assert” cognates (claim), bi-temporal table, statement,
time period.
event
Semantics:
a point in time or a period of time during which one or more objects
come into existence, change from one state to another state, or go out of
existence.
Comments:
Events are the occasions on which changes happen to persistent objects.
As events, they have two important features: (i) they occur at a point in
time, or sometimes last for a limited period of time; and (ii) in either case,
they do not change. An event happens, and then it's over. Once it's over,
that's it; it is frozen in time. (From Chapter 2.)
Components:
point in time, period of time, object, persistent object, state.
existence dependency
Semantics:
an object X is existence dependent on an object Y if and only if there
can be no point in time at which X exists but Y does not exist.
Comments:
Note the “can be”. If “is” were in its place, the statements would express a
correlation, but not a requirement.
Components:
assertion time, clock tick, effective time, episode, object, occupy,
version.
explicitly temporal data
Mechanics:
a row of data which contains an assertion time period and/or an
effective time period.
Semantics:
a row of data whose assertion time and/or effective time is expressed
by means of one or more columns of data.
Comments:
See also:
implicitly temporal data
.
Components:
assertion time, effective time.
external pipeline dataset
Mechanics:
a dataset whose destination or origin is one or more production
tables, and which is a distinct managed object to the operating system and/or
the DBMS.
Semantics:
a dataset whose contents are production data.
Comments:
Tabular data which will become part of the production database are
transactions acquired or generated by a company's OLTP systems.
