Information Technology Reference
In-Depth Information
Chapter 11
Linking Data and “Metadata”: Packaging
11.1 Information Packaging Overview
OAIS describes packaging at a high level, as outlined in
Sect. 6.3.4
, where it is
stressed that the package is a logical structure, i.e. does not have to be a single file.
Despite stressing the logical structure, it can be useful to package digital objects -
let's say files - together in a single file, for example a ZIP [
142
] file. However if
one simply did that then there would be no indication of the relationship between
the files, so there must be some mechanism for specifying the relationship. In any
practical system one needs to encode the links somehow.
If it is not practical to put everything into a single file then an alternative would
be to point to one or more of the digital objects using some kind of identifier system.
As in the single file case, one would need to specify the relationships somehow.
There are many ways of implementing this kind of packaging and each has its
own mechanism for specifying such relationships. Regarding the package as a dig-
ital object, another way of thinking about this is that one needs the appropriate
Representation Information in order to use the package - however it seems useful
to have some special terminology in this case.
One can imagine that these mechanisms for specifying the relationships between
the components of the package could include:
•
Naming conventions for the components
•
Reliance on specific software to extract the components
•
Indirection, for example by means of an XML schema which provides the seman-
tics to distinguish different components. Of course the schema would need its
own Representation Information, and in particular the semantics associated with
the element names.
•
General relationship techniques such as RDF - again there would need to be addi-
tional Representation Information meaning of the tags would have to be specified
separately.
There are a number of techniques which have been proposed including
IMS content packaging [
143
], SOAP [
144
], METS [
145
] and XFDU [
146
].
