Web services as building blocks for Science Gateways in Astrophysics

An efficient exploitation of the Distributed Computing Infrastructures (DCIs) is specially needed to deal with the data deluge that the scientific community, in particular the Astrophysics one, is facing. This requires a good understanding of the underlying DCIs. Science Gateways (SGs) provide the users with an environment that eases the interaction with the DCIs. As a previous step, IT skilled users should populate the SGs with friendly but advanced tools (e.g. workflows, visualization tools) that not only support the scientists to build their own experiments but also adapt them in an optimal way to the infrastructures. In Astronomy, the Virtual Observatory provides the community with services and tools for data access and sharing. However, state of the art telescopes and the coming Square Kilometre Array (SKA), able to reach data rates in the exa-scale domain, will also require advanced tools for data analysis and visualization that should be run on DCIs as well as shared on SGs. In the here presented work, we have selected as exemplar a set of analysis tasks of interest for some SKA use cases. These analysis tasks have been implemented as web services that use the COMPSs programming model in order to achieve a more efficient use of the DCIs. At the same time, the nature of the web services turns them into blocks that the astronomers can combine with VO services to build their own workflows. The web services and the workflows built upon them form a two-level workflow system that hides the technical details of the DCIs and exploits them efficiently. This approach is used for the first time in analytical tasks of interest for the SKA that benefits from the capabilities of the DCIs.