Databases Reference
In-Depth Information
Semantics:
to lock an asserted version row is to prevent it from being updated or
deleted without moving it into past assertion time.
Comments:
See also:
withdraw
.
A deferred transaction locks a row by setting its assertion end date to the
assertion begin date of the deferred assertion it creates. Rows that are
locked by means of deferred assertions remain currently asserted until
their assertion end dates fall into the past.
Components:
9999, asserted version table, assertion end date, Now(), past
assertion.
logical delete versioning
Mechanics:
a form of versioning similar to basic versioning, but in which
delete transactions are carried out as logical deletions, not as physical
deletions.
Semantics:
a form of versioning in which all versions of the same object are
contiguous, and in which no version is physically deleted.
Comments:
Logical delete versioning is not part of Asserted Versioning. See Chapter 4.
See also:
basic versioning, temporal gap versioning, effective time
versioning
.
Components:
basic versioning, contiguous, object, version.
maintenance encapsulation
Mechanics:
hiding the complexity of temporal insert, update and delete
transactions so that a temporal transaction needs, in addition to the data
supplied in a corresponding conventional transaction, either no additional
data, or else one, two or three dates representing, respectively, the effective
begin date of a version, the effective end date of a version or the assertion
begin date of an assertion.
Semantics:
the ability to express all temporal parameters on temporal
transactions declaratively.
Comments:
Maintenance encapsulation means that inserts, updates and deletes to
bi-temporal tables, and queries against them, are simple enough that
anyone who could write them against non-temporal tables could also
write them against these tables. (From the Preface.)
Components:
assertion, assertion begin date, conventional transaction, effective
begin date, effective end date, temporal transaction, version.
managed object
Semantics:
a named data item or collection of data that is manipulable by the
operating system, the DBMS or the AVF, and which references persistent
objects.
Comments:
For example, tables, rows, columns, versions and episodes are all
managed objects. Individual customers, clients or policies, while
examples of objects, are not examples of managed objects.
In the phrase “managed object”, the word “object”, by itself, has no
meaning. In particular, it has no connection with the technical term
“object”.
Managed objects are data which transformations and constraints treat as
a single unit. (From Chapter 5.)
Components:
reference, persistent object.
