Accessing the EGSO Grid through a WSRF-Enabled API

Andr´e Csillaghy, Marco Soldati, Philipp KunzDepartment of Computer Science, University of Applied SciencesNorthwestern Switzerland, CH-5210 Windisch, SwitzerlandRobert D. BentleyMullard Space Sciences Laboratory, University College LondonIsabelle SchollInternational Space University, Strasbourg Campus, FranceAbstract. EGSO is part of the Virtual Solar Observatory. It providesa Grid for integrated access to distributed and heterogeneous solar dataarchives. Here we describe the motivation and approach we have chosento implement the Grid access as a stateful web service. Using this kindof service allows us to consider the search and retrieval of data as aninteraction between the client and the Grid. This way, the EGSO servicecan be merged into interactive data analysis systems such as Python orIDL.1. EGSO in shortThe European Grid of Solar Observations (EGSO, www.egso.org, Csillaghy etal, 2005) just finished the production of a data grid middleware integrating theaccess to solar data. EGSO provides the fabric of a virtual solar observatory.Using EGSO, everyone can straightforwardly access many available solar ob-servations over the Internet. EGSO is an unprecedented service for the solarphysics community. In addition, this project also provides a test bed for datagrid research. Data grids allow exploiting the large potential of combining dis-tributed archives. In this context, the EGSO experience links the specific needsof the solar physics community with fundamental Grid research.EGSO allows querying in a unified manner distributed resources such assolar event and feature catalogs, observation catalogs and eventually retrievingthe associated observations. EGSO can be accessed in two different ways. Thefirst way is to use a web-based GUI. This allows a straightforward use of thesystem for inexperienced or occasional users. The second way is to use directlythe Application Programming Interface (API) on which the GUI is built. Thisis the subject of this paper.Using the API offers more flexibility than the GUI, and can provide com-plete access to the system from interactive environments such as IDL or python.1