Databases Reference
In-Depth Information
past assertion
Mechanics:
a row whose assertion end date is earlier than Now().
Semantics:
a row which represents a statement we are no longer willing to claim
is true and/or actionable.
Components:
actionable, assertion end date, Now(), represent, statement.
past episode
Mechanics:
an episode of an object whose latest version has an effective end date
which is earlier than Now().
Semantics:
the representation of an object in a period of past effective time which is
either [before] or [before-
1
] all other representations of the same object.
Components:
Allen relationship [before], Allen relationship [before
1
], episode,
effective end date, effective time, Now(), object, represent, version.
past version
Mechanics:
a version of an object whose effective end date is earlier than Now().
Semantics:
the representation of an object in a period of past effective time which
[
excludes
] all other representations of the same object, in shared assertion
time.
Components:
Allen relationship [
excludes
], effective end date, effective time, Now
(), object, represent, version.
pending transaction
Description:
an insert, update or delete statement that has been written but not
yet submitted to the applications that maintain the production database.
Sometimes pending transactions are collected outside the target database, in
batch transaction files. More commonly, they are collected inside the target
database, in batch transaction tables. (From the Preface.)
Comments:
Pending transactions are collected in batch transaction files. See also
external pipeline dataset, batch transaction file
.
As internalized by Asserted Versioning, they are those semantic
collections of asserted version rows called Pending History, Pending
Updates and Pending Projections.
PERIOD datatype
Mechanics:
the representation of a time period as a datatype.
Semantics:
the representation of a time period by a single column of data, a
well-defined set or range of values, and a well-defined set of operations on
those values.
Comments:
Several DBMS vendors, including Oracle and Teradata, have defined
PERIOD datatypes, but we do not know whether or not their definitions
are equivalent.
We would regard any PERIOD datatype as inadequate unless it could
express a time period with an unknown starting point or an unknown
ending point. We would regard DBMS support for any PERIOD datatype
as inadequate unless a unique index could be defined on any column
with a PERIOD datatype that would treat any two time periods as
duplicates if they shared even a single clock tick.
Components:
N/A.
persistent object
See
object
.
