Information Technology Reference
In-Depth Information
speaking, impossible to design a different file with a matching digest. This means
that if we can keep the (short) digest safely then we can use it to check whether a
copy of a (perhaps very large) digital object is what we think it is. This can be done
by recomputed the digest, using the same algorithm, using the digital object which
we wish to check. If the digest matches the original one we carefully kept then we
can be reasonably sure that the digital object does indeed have the same bit sequence
as the original.
3.2.2.5 Access Rights Information
Access Rights Information:
The information that identifies the access restric-
tions pertaining to the Content Information, including the legal framework,
licensing terms, and access control. It contains the access and distribution con-
ditions stated within the Submission Agreement, related to both preservation (by
the OAIS) and final usage (by the Consumer). It also includes the specifications
for the application of rights enforcement measures.
Access rights and digital rights are discussed further in Sects.
10.6
and
17.7
.
Examples of PDI from different disciplines are given in
Table 3.1
.
3.2.3 Linking Data and “Metadata” (Packaging)
The idea behind packaging is that the one must somehow be able to bind the various
digital objects together. Remember also that Content Information is the combi-
nation of Data Object plus Representation Information, and PDI has its various
components. Fig.
3.5
shows the other conceptual components of a package.
The package does not need to be a single file - it is very important to understand
this. It could be, but it does not have to be. The package is a logical construction,
in other words one needs to be able to have something which leads one to the other
pieces, by one means or another. About the package itself one needs to be able to
identify it i.e. is it a file, a collection of files, a sequence of bytes on a tape? The
information which provides this is the Packaging Information.
Packaging Information:
The information that is used to bind and identify the
components of an Information Package.
For example, it may be the ISO 9660 vol-
ume and directory information used on a CD-ROM to provide the content of several
files containing Content Information and Preservation Description Information. For
a ZIP file it would be the information that the package is the file which probably has
a name ending in “.zip”.
In addition the package contains something and the Package Description provides
the description of what this is; it is something that can be used to search for this
particular package.
