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2.1 Preservation strategy
VERS ensures continued access to the content of electronic
records by converting the content to a long-term preservation format. The
selection of a long-term preservation format is based on the following
considerations:
-
The format captures the essential characteristics of the original
format. For PROV, the essential characteristic is that the long-term
preservation format captures how the original user saw the record.
-
That it is possible to re-implement a program to display the
format from a specification. The worst case scenario is that a technician is
required to implement a program from scratch with, initially, no other
information than that contained in a VEO. In order to do this, they will
require to be able to:
-
identify the format. This information is contained in metadata
within the VEO. (Specifically these elements are M128 File
Encoding and M131 Rendering
Text. Further information about these elements is contained in PROS 99/007
Specification 2: VERS Metadata Scheme, and its associated Advice.)
-
obtain a copy of the specification of the format. Normally, we
would expect this specification to be in the form of a published document
available from a library (or archive). Note that it is necessary to ensure that
the software vendor supplying the program actually followed the specification;
it is not unknown for vendors to unofficially extend the specification or not
to implement it accurately.
The VERS Standard does not specify when the content of a record is to be converted to the
long-term preservation format. It must be converted by the time of export to
PROV, but it may be converted at any time prior to this.
The challenges with conversion are:
-
ensuring that it is possible to convert the original. There are
many reasons why it may not be possible to convert upon export. These include
the lack of a suitable program to display the original content (e.g. the
program may have been discarded, or may no longer run), or the file may be
encrypted or protected by a password and the access key has been lost.
-
ensuring that the conversion retains fidelity with the original.
The main reason for loss of fidelity is simply that the conversion is being
performed by a different program (or a different version of the program) than
that used by the original creator of the record. A subsidiary issue of ensuring
conversion fidelity is being able to demonstrate the fidelity of conversion.
This is equivalent to ensuring, for example, that a microfilming or digitising
project produces clear images of the original paper records.
Both of these challenges occur whenever the conversion occurs,
but the challenges may be more severe the later that conversion occurs.
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