Information Technology Reference
In-Depth Information
to physically package Representation Information with the data content, in the
Archival Information Package (AIP). However for any piece of information,
changes in the knowledge base of the Designated Community imply that the amount
of Representation Information which has been explicitly captured must change, and
this is facilitated by being able to point outside of the AIP.
In order to tie this in with the idea of the initial piece of Representation
Information, we can expand the first transaction as follows:
The initial RepInfo (a RepInfoLabel) is circled in Fig.
17.4
; if the applica-
tion needs some Semantic RepInfo, then the appropriate CPID is selected and the
piece of RepInfo (something to do with Semantics) is obtained from the Registry/
Repository and transferred back to the user. This piece of Semantic RepInfo may
be understandable by the user; if not then it will itself have a CPID associated with
it which points back to the Registry/Repository - to another RepInfoLabel. This
iteration continues until the user can understand the RepInfo.
Note that the CASPAR “RepInfoLabel” itself has Representation
Information. The RepInfoLabel has been introduced for convenience,
but is not in any sense unique or irreplaceable.
Another possible termination point is indicated by the CPID having the spe-
cial value “MISSING”, which indicates that the Representation Information is not
available - and this could signal that there is a RepInfo gap.
CPID
Structure = CPID
Semantics = CPID
Rendering s/w = CPID
Each “bag of
bits
”
has an
associated
pointer (
CPID
) to
a Label
Label
−
points to other
RepInfo
copy
CPID
Structure = CPID
Semantics = CPID
Rendering s/w = CPID
CPID
External Registry
Fig. 17.4
Use of repInfoLabel
