Introduction to Science Gateways and Science Gateway Frameworks - Science Gateways for Distributed Computing Infrastructures - page 4

comprehensive and sophisticated work ows for the community and hiding these

complex work c user interface. The

advantage of this approach is that the DCI access services are already solved and
provided in a robust way by an SG framework, and hence the user communities can
concentrate on producing their application-speci

ows behind a simpli ed application-speci

c layers of the science gateway. In
this way the redundancy of developing the same DCI access mechanisms by many
different communities can be avoided. For the same reason, the development time
of SG instances can be signi

cantly reduced, and there is a good chance that within
the lifetime of the requiring project the science gateway can be built and provided
as a production service. Another advantage is that the cost of producing such a
gateway is usually lower than in the case of the first approach. Since the gateway is

a customization of an existing robust and scalable SG framework, the resulting
production SG instance will also be robust and scalable. The sustainability of such
an SG instance is more certain than in the case of the

first method since the large set
of user communities involved in the adaptation and maybe further development of
the framework represents a strong lobbing force to get further funding for main-
tenance and development. It is also important that the gateway framework should
be open source and should involve community members in the development and
maintenance of the code. When the SG framework is sustainable, the community of
the SG instance should maintain only a narrow set of user-speci c services, and the

rest should be maintained by the SG framework developer community.

1.2 Architecture of Science Gateways

In both SG frameworks and SG instances two main components should be
distinguished:

Front-end

￿

Back-end

￿

The role of the front-end is to provide the necessary user interface. In the case of
SG instances the interface is very much customized to the particular needs of the
scienti c user community. For example, chemists and biologists would like to see

visualization tools for molecules, whereas meteorologists need various types of map
visualizations. The major focus of SG instances should be to develop this kind of
specialized user interface to provide the right front-end for the target user com-
munity. In the case of an SG framework the interface is typically more generic,
providing user interface for generic features that might be needed for many different
user communities and SG instances. For example, these could include user inter-
faces for certi

cate management, file and data management, job submission,

work ow creation and management, monitoring, etc. These generic parts of the

front-end could also be reused from an SG framework for the implementation of
customized SG instances. Quality requirements for a front-end are as follows: