Code Manual for CONTAIN 2.0 - Federation of American Scientists

instruction set that creates the variant will work only on that particular base code, because other
versions of the base code will have different line sequencing.
As time passes, the base code evoIves away from the variant code, and cross-fertilization between
the two variations becomes desirable. Code features are transferred in two ways:
1) from the variant version to the base code, and
2) from the base to the variant version.
Staff in the base code project determine whether or not to carry out a transfer of the first type based
on a strict costhenefit assessment done from the viewpoint of the base code project sponsor. They
then implement the desired changes in essentially the same way that a code revision is done, by
assigning the update a location in the sequencing of code changes, modifying the code
documentation, and completing formal testing.
A similar assessment from the viewpoint of the variant code project is done for the second type of
transfer. The desired changes are accomplished periodically and systematically by a process called
an “accommodation.” Using this method, an update set that creates an existing, working variant
version from a particular base code is modified to reflect the line numbering of a subsequent base
code release. This part of the process is straightforward. In addition, it is usually necessary to
examine the interactions between features in the variant code and new features in the base code that
have developed after the original base version was frozen. Some features may have to be disabled
and/or significantly reworked. When complete, the accommodation wiII provide anew variant code
that has the original variant features, and those new features in the base code that were deemed
appropriate. The cost of performing this accommodation is borne by the variant code project.
Note that at times the variant code based on one release of the base code coexists in time with a later
release of the base code. This situation occurs because it takes time to perform an accommodation,
and also because there may be reasons to postpone an accommodation until a natural point in the
variant development schedule occurs. The relationship between the mainstream CONTAIN code and
vtiant versions of CONTAIN is shown in Figure D-8.
Documentation of variant versions using this approach can be simplified by providing supplementary
reports that discuss the differences between a variant release and the documented base version from
which it stems. This was done for CONTAIN-HWR. [Bi194]
D.2.6 Testing
Testing verifies the integrity of both individual updates and code revisions and of the combination
of revisions that becomes a new version. Testing has four objectives: verification, validation,
integration, and regression prevention. The objective of verification is to determine that the update
set performs as specified by the code developer in the code specification requirements. Validation
testing determines that the update set performs calculations accurately with respect to the physical
model represented. Validation testing may include comparison of calculated results with available
Rev. O D-15 6/30/97