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a CORBA client applet
that permits the access via any Web browser. This client is integrated
in a standard Web page and exploits both the CORBA support embedded in
the most diffused Web browsers (e.g. Netscape Communicator 4.x or higher)
and the simplicity of the integration between Java and CORBA. Though the
connection between this client and the MADAMA server is transparently
maintained by the CORBA infrastructure, the client applet cannot take
advantage of the distributed infrastructure of intermediate active hosts.
For this reason, this client is a lightweight one, that
simply allows an authenticated user to select the interested film for
user visualization. Figure 1 shows the CORBA
interface of MADAMA servers that is used in the CORBA light client applet.
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Figure 1. MADAMA Internal CORBA Interface for the Client Applet
(click
here for a larger view of the picture) |
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a MADAMA proprietary client
that fully exploits the flexibility of the MADAMA infrastructure. This
full client allows users to specify the required QoS level
and to modify requests during service provision, and is able to connect
to the dynamically determined chain of intermediate hosts along the path
from the client to the selected server. The client is currently implemented
in Tcl/Tk, but we have also recently realized (and now testing)
a completely analogous one in the Java language by exploiting
the Java Media Framework functionality. The MA technology
has permitted us to enlarge the accessibility of this client also from
hosts that do not own its code. It is possible to request the client
dynamic installation via a Web form (Figure
2 and Figure 3): this action triggers the
migration of an installation agent that carries the Tcl/Tk
code of the proprietary client from a code server to the client host.
After migration, the installation agent saves the client on the local
disk, sets up the necessary system variables of the hosting environment,
sets up some parameters of the client according to the host machine (video
and audio resolution supported), and runs the client. When the multimedia
flow of the selected film has terminated, the agent asks the user whether
to cancel the installation or to maintain the full functionality client
for successive sessions of the MADAMA service.
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Figure 2. Web Request for MA-based Installation of the Madama Proprietary
Client
(click
here for a larger view of the picture)
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Figure 3. The MADAMA Proprietray Client GUI
(click
here for a larger view of the picture)
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