Information Technology Reference
In-Depth Information
<sdf:block>
<sdf:encoding>BINARY</sdf:encoding>
</sdf:block>
</xs:appinfo>
</xs:annotation>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:element>
Here the CDF element, the first item of interest in the file, is binary information
and represented as a 3 byte character string, the VERSION_BYTE is described as
simply being one unsigned Byte. Part of the more complete XML schema structure
of the NetCDF file is shown below however the complete description is quite lengthy
and so not shown.
Using the DRB engine
http://www.gael.fr/drb/features.html
open source soft-
ware created by Gael, it is possible to use the XML Schema description as an
interface to the underlying data. The software supports access and querying of the
described data using the XQuery XML accessor language. For example to access
the CDF and the VERSION_BYTE one could have a query like the following
<magic id
=
"{/netcdf/header/magic/CDF}"
version
=
"{/netcdf/header/magic/version_byte}"/>
More complex queries have been created to access the data sets contained within
the file.
There is also BNF format description located in the unicar website for
NetCDF
http://www.unidata.ucar.edu/software/netcdf/docs/netcdf/Classic-Format-
Spec.html#Classic-Format-Spec
however this is purely for documentation and
cannot be used as an interface to the underlying data.
7.7.3 Rendered
The image described in Sect.
7.7.1
is a rendered object.
Other rendered objects are, for example, Web pages. Here the Representation
Information would include the HTML standard [
66
]. We may have this stan-
dard in the form of a PDF, written in English, thus the Representation Network
would include descriptions of these, or specify them as part of the Designated
Community's Knowledge Base.
7.7.4 Non-rendered
Digital Objects which are not normally rendered would by definition be non-
rendered, but as noted the boundary is not always clear-cut. As discussed in
Sect. 4.2
