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Figure 6. The architecture of cloud supporting DRSC model
a text file. The format of the text file corresponds
to the properties of the five atomic DRSC com-
ponents. The data in the text file is imported to
the clouds by invoking the web services of the
DRSC object.
In short, this architecture provides users with
the flexibility needed to build an institutional re-
pository. Users can set up the component services
on local servers or just use available cloud services
on the Internet. That is the advantage of the SCA
model: you can call a service through different
protocols. The clouds are the key components to
build an institutional repository. Of course, the
availability and quality of the cloud services will
affect the application very much. We will introduce
the architecture and functions of them below.
the structures of the clouds themselves are also
based on SCA. As shown in Figure 6, there are
seven layers: network infrastructure layer, data
layer (including Relational Database - RDB, XML
database and file sets), data access layer, logic
layer, ESB layer based on SCA, event response
layer and user interface layer.
To further describe Figure 6, the network in-
frastructure layer provides the basic communica-
tions. There are three kinds of data storage
mechanisms. The first is the relational database
which is used to store the common and fixed
structured information such as login name, pass-
word and Dublin Core metadata, as the change
of the RDB structure will bring too much modi-
fication for the application. The second storage
mechanism is the XML database which is used
to store the changeable data such as the specific
metadata of a digital resource that are semi-
structured, as the schema of an XML file is easy
to be extended. The third storage mechanism is
the file set which is used to store unstructured
data such as image, audio and video resources.
In the design of a DRSC object, these three
kinds of data have to be clearly classified. For
5. DESIGN AND IMPLEMENTATION
OF THE CLOUDS
The Clouds can be distributed across the Internet
and provide the functions of accessing and ma-
nipulating the data. Similar to the architecture of
the Institutional Repositories built on the clouds,
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