Information Technology Reference
In-Depth Information
Chapter 4
Types of Digital Objects
There are more things in heaven and earth, Horatio, than are dreamt of in your
philosophy.
(
William Shakespeare
, “Hamlet”)
There are many types of digital objects which we may come across and we need to
recognise the extent of their diversity otherwise we will aim too low when we design
our tools and techniques for digital preservation.
It is impossible to give an exhaustive list of types of digital objects, yet it is use-
ful to remind ourselves of at least some of the great variety that we must be able
to deal with. By
types
we mean not just different formats, but rather different
classifications.
One reason for being interested in the variety of types is that unless one is aware
of the distinctions it is very easy to assume that everything is the same and the
same tools can be used. For example if one normally deals with the preservation
of documents, for example Word or PDF, then one might assume that all digitally
encoded information can be preserved using the same tools. Unfortunately this is
not true, as we will see. The next sections present a brief overview of some of the
distinctions which can be made, without any claim of being exhaustive.
4.1 Simple vs. Composite
One way to classify digital objects is by whether they normally are treated as a
whole - for example an image such as Fig.
4.1
- or whether they are normally
treated as a collection of simpler parts, for example a FITS file which has several
images and tables, as in Fig.
4.2
. The latter we will call Composite Objects (or
sometime Complex Objects).
It is important to make this distinction because if we can break the preserva-
tion challenge of a composite object into smaller components then it will make the
preservation task easier. On the other hand if we treat the composite object as if it
were a simple one then we could run into a great deal of trouble in future.
