Introduction to Science Gateways and Science Gateway Frameworks - Science Gateways for Distributed Computing Infrastructures - page 5

￿ User-friendliness : provides intuitive user interface.
￿ Ef ciency : provides fast response time even for complex user requests.
￿ Scalability : provides fast response time even for a large number of simultaneous
user requests.
￿ Robustness : keeps working under any circumstances and recovers gracefully
from exceptions.
￿ Extensibility : it must be easy to extend with new interfaces and functionalities.
Notice that the main dif culty of building an SG front-end is not the pretty

design of the user interface but the achievement of the quality requirements listed
above. These become really important when the SG is used in production by a large
number of scientists. Gateways created from scratch in many cases reach only the
prototype level, or if they go into production, they face a lot of dif

culties to meet

these quality requirements.
The back-end provides the necessary DCI access mechanisms that are needed to
realize the typical gateway functionalities like certi

cate management, file and data

management, job submission, work ow management, monitoring, etc., for various

DCIs. The back-end is typically generic, i.e., the same back-end can be used by
many different SG instances. Therefore the main advantage of developing SG
frameworks and deriving the SG instances for them appears in the field of devel-

oping the back-ends. If a generic back-end is developed in a robust way by an SG
framework, all the SG instances derived from it can take the benefit from its
robustness with no or little development effort. A good back-end can support
several DCI types (clusters, grids, desktop grids, clouds, etc.); therefore one of the
distinguishing features of SG frameworks is how many different DCIs they can
support and how easily these DCIs can be accessed via the functionalities provided
by the SG framework.
Quality requirements for a back-end are similar to the front-end requirements,
although their meaning could be quite different since the front-end serves users and
the back-end manages jobs and service calls:

￿ Ef ciency : provides fast response time even for complex submitted jobs or
service calls.
￿ Scalability : provides fast response time even for a very large number (even for
millions) of simultaneously submitted jobs or services calls.
￿ Robustness : keeps working under any circumstances and recovers gracefully
from exceptions.
￿ Flexibility : ability to manage many different types of DCIs and many concrete
instances of DCIs.
￿ Extensibility : it must be easy to extend with the support of new types of DCIs,
with new concrete DCIs, and new back-end services.