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Registry/Repositories, thus sharing preservation efforts within and across commu-
nities. We outline the modelling process briefly here. The process used within the
CASPAR project is described in more detail elsewhere [ 182 ].
The approach to preservation network modelling is based upon the idea of
making logical statements about what is known about the preservation resources
available, consisting of digital objects and the relationships between them.
The objects are uniquely identifiable digital entities capable of independent
existence which possess the following attributes:
Information - exposed through preservation analysis, this is the information
required to satisfy the preservation objective for the designated community
Location - information required by the consumer to locate and retrieve the digital
object.
Status - describing the form of a digital object, such as version, variant, instance
and dependencies.
Risks - detail the inherent risks and threats to the digital information. These may
include for example the interpretability of the information, technical dependen-
cies, loss of skills over time by the designated community.
Termination - the scope of the network up to the point at which no additional
information is required by the Designated Community to achieve the preservation
objective.
The relationships are modelled to capture an idea of how the information will be
utilized to achieve the preservation objective within the Designated Community.
Therefore it is important to model:
Function - a digital object being modelled will be used to perform a spe-
cific function or action, producing a preservation outcome, for example rep-
resenting the physical binary data as textual
information understood by a
human.
Tolerance - not every object having a function is critical for the fulfilment of the
preservation objective, some objects maybe included to enhance the quality of
the solution or facilitate the preservation solution.
Quality Assurance - the reliability of the object to perform the specified function
to a sufficient quality may be recorded for the relationship.
Alternate and Composite relationships - The case may exist where multiple
relationships within the network must function concurrently for a preservation
objective to be fulfilled or it may be that only one of many needs to function. In
Chap. 8 this was terms conjunctive and disjunctive dependencies.
If we take the following example from [ 183 ], the preservation objective was set as
follows:
A user from a future designated community should be able to extract a specific
set of parameters from data files for a given time and altitude.
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