Information Technology Reference
In-Depth Information
or experience - which can apply no matter what the difference in time - and is
necessary for usability by a wider community.
This is a very important consideration which should help to justify the expendi-
ture of those resources in preservation.
9.1.1 Relationship Between Preservation and (Re-)Use
Preservation of digitally encoded information requires that it continues to be usable
and understandable by a Designated Community. This has been extensively dis-
cussed in the previous chapters. A Designated Community is defined by the
repository (see
Sect. 6.2
) and this definition is vital for the testability of the effec-
tiveness of the preservation activities of the archive. However the point to realise
is that the Representation Information Network can (perhaps easily) be extended
to that needed by another Designated Community - or perhaps more precisely, to
match the Knowledge Base of some other user community, for immediate use.
In other words although the digitally encoded information is not guaranteed by
the repository to remain usable by these other users, by making the Representation
Information required to fill the knowledge gap explicit, this is much more likely
to be the case. Moreover the types of Registry/Repository(ies) of Representation
Information which are described in this topic will make it much easier to share the
Representation Information required. The repository holding the data does not itself
have to fill the gap; it needs to make it clear what the end points of the Representation
Information Network it can provide are.
This is not to say that everything becomes trivial. It is instructive to look at a
number of possibilities. One can first consider a single data object - which may
of course consist of several bit sequences (for example several files). After this the
implications for combining digitally encoded information may be analysed.
9.1.2 Digital Object Used By Itself
A digital object may be used by itself, for example a user may simply want to find
a particular fact from a dataset. For the sake of concreteness let us say that (s)he
wants to determine the photon counts at a certain position in the sky from data
captured by a particular astronomical instrument, and that data is held in a FITS
file. Other examples could include determining the character or the font used at a
particular position, say “the 25th character of the second paragraph of page 51”, in
a document. These are in many ways the simplest pieces of information which one
might wish to extract from a digital object. However if one can do this then one can
build up to the extraction of more complex pieces of information, using the concepts
of virtualisation discussed in
Sect. 7.8
.
The Representation Information Network (RIN) (Fig.
9.2
- an annotated version
of
Fig. 6.4
) indicates that a Java application is available to extract the numbers from
