Authenticity - Advanced Digital Preservation - page 217

audience's (i.e., designated community) knowledge base or be defined elsewhere
within the Information Object.
OAIS, as described earlier, proposes that to ensure preservation, one must have
enough Representation Information to allow the defined Designated Community
to understand the information, given that Designated Community's knowledge
base. This must include, for example, information used to expresses value of a
Significant Property. This is consistent with the comment “As with file formats,
the Representation Information for a digital object should allow the recreation of
all the significant properties of the original digital object” from the PARADIGM
project [ 161 ].
It should be noted that even those studies of Significant Properties which include
Designated Community only have it as an optional item and for example [ 162 ] states
“ By leaving the Designated Community value blank, the archive declares that the
property is, as far as they are aware, important for all user communities ”. Thus the
stress in this usage is on “importance”. It leaves open the issue as to whether the
value of that Significant Property is understandable to that very broad Designated
Community.
Comparing the various definitions only [ 156 ] includes “meaning” in its defini-
tion, and therefore seems somewhat out of step with the other definitions; [ 153 ]
includes what might be interpreted as a more ambitious phrase “ complete (for the
intended Consumer) intellectual content ”; [ 156 ] is the only one to include “acces-
sibility ”. Both [ 155 ] and [ 156 ] include “usability” in their definitions which is
plausible but hard to see, for example, with “redness”. The terms “appearance” and
“experienced” is used in [ 163 while [ 155 ] includes “rendering” and “behaviour”;
[ 154 ] refers to “rendered content” and, as noted above, the example in [ 153 ] makes
it fairly clear that the rendering is the main concern.
With such a diversity of definitions and a seeming clash with the OAIS defi-
nition of preservation, what is the real purpose of Significant Properties? In order
to explore this, we first discuss a number of important related concepts which are
identified within OAIS.
13.6.2 Authenticity and Significant Properties
Given that to be able to judge authenticity requires evidence, we note that some
of this evidence is technical, for example Fixity, and some of the many types of
Provenance are non-technical in the sense that they tell one how trustworthy an indi-
vidual is or was regarded to be. As noted above, if the bit sequences are unchanged
then there are well established mechanisms for checking this although, of course,
issues arise over the long term as to, for example, the security of any particular
message digest algorithm.
If however the bit sequences of the digital object are changed then these mech-
anisms are ineffective. For example a Word file may be converted to a PDF; in
that case the bit sequences will have been changed extensively. In such cases