18.104.22.168 Methodologies Involving Source Code Availability
The OAIS response to preserving an Access Software application execution service would likely depend, in part, on whether or not it had the source code for the application. If the OAIS had the source code and adequate documentation on the application, the expected approach would be to port the application to the new environment and attempt to test it adequately to ensure it was functioning correctly. As described in 4.2, it may not be obvious when the application runs but functions incorrectly. Ideally all possible output values would have been recorded initially so they could be used as the basis for ensuring correct functioning following the port. However, this level of testing is likely to result in an unacceptable cost/benefit ratio for the OAIS. Given that the application was compiled from original source code, it is probable that the algorithms are correct; the production of a test suite, or reuse of a test suite that was provided with the design documentation is probably adequate. As long as there is independent Representation Information for the Content Data Object, no migration need be involved.
If the Access Software was a proprietary package, which was widely used and available commercially, it is likely that there will be commercially provided bridge (i.e., conversion) software which Transforms the current Content Data Objects to other forms used by the new Access Software having a similar look and feel. This would be a Transformation type of Migration that is likely to be Non-Reversible. If no commercial alternative is seen, the OAIS may contract with the owner of the original Access Software to develop and provide source code for a simplified tool that can read but not modify instances of data written using the format. This would also be a Transformation type of Migration because of the change in software that is providing much of the Representation Information. This approach might not be viable because of cost or legal issues. In any of these cases, the OAIS will need to establish mechanisms to verify that no preserved information has been lost. This requires that criteria have been established to clearly define what constitutes the Content Information as discussed in section 6. In addition the OAIS must investigate the issues of ensuring that the new Access Software is available to the Designated Community.
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