Authenticity - Advanced Digital Preservation - page 220

The normal library practice of ignoring, by default, Semantic Representation
Information, has allowed Significant Properties, as usually considered without atten-
tion to meaning of their values, to appear to play a more general role in preservation,
to the detriment of the full use of the Representation Information concept. It is
only when looking at a broader class of digital objects, including scientific data and
software, and a broader definition of preservation, that their true role may be seen.
For any Significant Property some aspect of the information object has been
encoded in a way which is described by Representation Information (often struc-
tural). However to be useful to the designated community the meaning associated
with this property's value must also be available in their knowledge base. If the
knowledge base changes then appropriate additions should be made in the informa-
tion object's Representation Information to again ensure understandability by the
designated community.
On the other hand the Representation Information of an information object by
itself does not provide much direct guidance as to what Transformation to apply. The
transformation will usually alter the digital object and certainly new Representation
Information must be provided.
Clearly one could check that any new digital structure provided the capabili-
ties needed to support the semantics of the information object. However Significant
Properties provide a much simpler, albeit incomplete, way of choosing an appropri-
ate transformation, consistent with their use in a number of testbeds [ 165 ]. In addi-
tion Significant Properties do provide hints on how the Designated Community has
been defined (implicitly or explicitly) and the types of Representation Information
which must be present. In these ways the use of Significant Properties could
supplement the role of Representation Information.
13.6.4.1 Relationship to OAIS Concepts
In the updated version of OAIS the term Significant Properties is not explicitly
defined because it was felt that this would simply add to the already extensive
and inconsistent list of definitions for this term. Instead a number of inter-linked
definitions are provided, which are introduced here with some explanatory text.
The Significant Properties concept, however loosely defined, leads one to think
that there are “Insignificant Properties” i.e. properties which can be ignored from
the preservation point of view. Therefore OAIS introduced the concept of an
Information Property and its associated Information Property Description:
Information Property: That part of the Content Informationas described by
the Information Property Description. The detailed expression, or value, of that
part of the information content is conveyed by the appropriate parts of the Content
Data Objectand its Representation Information.
and
Information Property Description: The description of the Information
Property. It is a description of a part of the information content of a Content
Informationobject that is highlighted for a particular purpose.