Information Technology Reference
In-Depth Information
Increasingly one finds research papers, for example in on-line journals, which
have links to the data on which the research is based. In such a case some or all of
the above issues may threaten their survival.
Another peculiarity of digital data is that it is easy to copy and to change.
Therefore how can one know whether any digital object we have is what it is claimed
to be - how can we trust it?
A related question is - how was a particular digital object made? A digital object
is produced by some process - usually some computer application with certain
inputs. In fact it could have been the product of a multitude of processes, each
with a multitude of input data. How can we tell what these processes and inputs
were, and whether these processes and inputs were what we believe them to have
been? Or alternatively perhaps we want to produce something similar, but using a
slightly changed process - for example because the calibration of an instrument has
changed - how can this be done?
To answer these kinds of questions for a physical object, such as a velum
parchment or a painting one can do physical tests to give information about age,
chemical composition or surface contaminants. While none of these provide conclu-
sive answers to the questions, because one needs documentation about, for example,
the chain of ownership of paintings, but at least such physical measurements pro-
vide a reality check. None of these techniques are available for digital objects. Of
course these techniques can be applied to the physical carriers of the bits, but those
bits can usually be changed without detection. One can think of technologies - for
example the carvings on stone - where it might be easy to detect changes in the bits
by changes in the physical medium, but even if no changes are detected one is still
not certain about whether it is what is claimed..
One often hears or reads that the solution to all these issues is “
meta-
data
” i.e. data about data. There is some truth in that but one needs to
ask some pertinent questions not the least of which are “what types
of 'metadata'?” and “how much 'metadata'?” For example it is clear
that by “metadata” many people simple refer to ways of classifying
or finding something - which is not enough for preservation. Without
being able to answer these questions one might as well simply say we
need “extra stuff”.
Much of the rest of this topic is about
the multitude types of
“metadata” that is needed.
We will put the word in italics and quotes when we use it - “metadata”
- to remind the reader to be careful to think about what the word
means in its particular context.
Much of the rest of this topic aims at answering those two questions, namely:
•
what types of “metadata” are needed?
and
•
how much of each of those types of “metadata” is needed?
