Basic Preservation Strategies - Advanced Digital Preservation - page 199

12.2.1 Access and Use Services
OAIS discusses maintaining the Dissemination API in order to continue to support
applications which the Designated Community uses to access and use the digital
object. This is closely related to the ideas of virtualisation discussed in Sect. 7.8 .
The virtualisation approach has the advantage that it facilitates the ability of the
Designated Community to be able to use their favourite applications to access and
use the digital object. This can be consistent with maintaining the Dissemination
API by means of appropriate software wrappers. A number of options are discussed
in some detail in Chap. 9 .
12.2.2 Access Software Look and Feel
This option focuses on the assumption that the Designated Community wishes to
maintain the original “look and feel” of the Content Information of a set of AIUs as
presented by a specified application or set of applications. Discussion of hardware
emulation, which provides the ultimate maintenance of look and feel is provided in
Sect. 7.9 . Conceptually, the OAIS provides (i.e. makes available/points to) a soft-
ware environment that allows the Consumer to view the AIUs Content Information
through the application's transformation and presentation capabilities. For example,
there may be a desire to use a particular application that extracts data from an ISO
9660 CD-ROM and presents it as a multi-spectral image. This application runs under
a particular operating system, requires a set of control information and use of a CD-
ROM reading device, and presents the information to driver software for a particular
display device. In some cases this application may be so pervasive that all members
of the Designated Community have access to the environment and the OAIS merely
designates the Content Data Object to be the bit string used by the application.
Alternatively, an OAIS may supply (as Representation Information) such an envi-
ronment, including the Access Software application, when the environment is less
readily available. However, as the OAIS and/or the Designated Community moves
to new computing environments, at some point the application will cease to func-
tion or will function incorrectly. At such a point Transformation will become an
attractive option.
12.2.2.1 Emulation of Look and Feel the Hard Way
It is worth discussing in a little more detail another way of maintaining look and
feel when, for example the compiled version of the application or libraries it depends
upon, are not available, nor is the source code. The term emulation may be applied to
this technique since emulation may be defined as “ the ability of a computer program
or electronic device to imitate another program or device ”[ 79 ].
The OAIS may, despite the drawbacks, consider emulation for the access applica-
tion in the following way. If the application provides a well-known set of operations
and a well-defined API for access, the API could be adequately documented and