Use of the TANGO Interactive Collaboratory Tool in the CEWES MSRC PET
Program

By David E. Bernholdt, Nancy J. McCracken, Marek Podgorny, and
Geoffrey C. Fox

The DOD Research and Development community is widely distributed
geographically.  This presents quite a challenge to providing
researchers with access to training on HPC systems and technologies,
and to professional education in computational science, two important
aspects of the PET program.  Distance education is not a new idea, but
it often requires specialized equipment (such as satellite uplinks and
specialized videoconferencing systems) or doesn't provide the level of
interactivity many students desire (i.e. videotaped lectures).
However it is now becoming possible to routinely deliver deliver
courses in real-time over the Internet.  TANGO Interactive, developed
at the Northeast Parallel Architectures Center at Syracuse University,
an academic partner in the CEWES MSRC PET program, is a network-based
collaboratory tool which is currently being used for remote education
and training activities, and will soon be made available to users of
the CEWES MSRC for more general collaborative use.

Tango provides a framework which allows applications to be shared
remotely over the network, not just for education, but for any kind of
remote collaboration.  The Tango system has a client-server
architecture, in which the clients consist of a Control Application
and a variety of shared applications.  The Control Application handles
administrative functions, such as launching applications and tracking
which users are sharing each application.  Collaborative applications
send "events" to the Tango Server, which then rebroadcasts them to
other clients sharing the application. Apart from a few basic
functions, the developer of the application is free to define whatever
shared events which are appropriate to their application.  If
communications performance is critical, clients may also communicate
directly, bypassing the server.  Tango also provides a basic form of
"floor control" by keeping track of a simple master/slave flag for
each instance of a shared application, and providing a mechanism to
grant and relinquish master status.  However once again, the
application developer can interpret this flag as appropriate for their
particular application, so that a chat tool need not be forced to
follow a master/slave model which doesn't make sense, while a
whiteboard application can choose to use it to control "passing the
pen" among participants.

From the client side, the principle access to the system is through a
web browser, which allows the Control Application and other Java
applets in the package to be loaded on demand.  Although many shared
applications are written in Java, they need not be. Clients have also
been written in C, C++, and even Lisp (for a shared Emacs editor).
The application program interface (API) for the Tango system is
public, and users are encouraged to port existing tools to Tango or
develop new ones as their needs require.  Tango was originally
developed under a contract from the Air Force's Rome Laboratory for
use in a Command and Control/Emergency Management scenario, which
included shared visualization of terrain data extracted from a GIS
system, and other groups are using Tango as the collaborative
framework to share a variety of other applications.

As far as Tango is concerned, distance learning is just a special case
of electronic collaboration, in which a Shared Web Browser, or similar
Tango application is used to show course materials served by a
standard web server.  Tango conveys the URLs (the Shared Browser's
"events") to the student browsers each time the instructor clicks on a
hyperlink, and the student browsers respond by loading the page from
the web server (see Figure 1).  Syracuse faculty have used this
approach to deliver three fully-accredited semester-long courses in
computational science to students a PET partner Jackson State
University in Mississippi, with several CEWES staff auditing this
semester's graduate-level course at the CEWES MSRC TEF.  The approach
is also being introduced into the PET Training program through a
series of prototype distance trainings in collaboration with the Ohio
Supercomputer Center, another PET partner.

These PET initiatives are helping to transfer collaborative
technologies into the DOD Research and Development community to reduce
the "importance of place" in access to training, education, and
general collaboration.



Figure 1. The architecture of the Tango-based distance education
project with Jackson State University in Jackson, Mississippi.
Lecturer's Shared Browser uses Tango to convey URLs for course
materials to student Shared Browsers, which then retrieve the page
from a standard web server.