CTWatch
November 2005
E-Infrastructure: Europe Meets the e-Science Challenge
Mike Boniface and Colin Upstill, University of Southampton IT Innovation Centre

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SIMDAT Architecture

All application sectors deploy existing problem-solving environments for product and process design. Each application activity in SIMDAT is integrating Grid middleware into existing applications to provide a demonstration of distributed, collaborative work in complex problem solving. The vendors of these environments require an acceptable level of stability in middleware technology before it will be adopted with their products and delivered to customers. Well-designed and accepted standards are essential for technology uptake.

Examining Grid infrastructure state-of-the-art, it is clear that even the core technology, which underpins higher-level services such as resource and execution management, is still evolving. In the future, core features should be part of a standards-compliant architecture, so application developers can use them more easily and so they can choose between different interoperable Grid implementations.

The Open Grid Services Architecture2 (OGSA) represents an evolution towards a Grid system architecture based on Web services concepts and technologies. OGSA Profiles for various higher-level functions are beginning to be developed but there are certainly no OGSA compliant grid implementations. Even the underlying proposed standard WS-Resource Framework3 (WS-RF) is still somewhat controversial and has yet to prove its value. Therefore, the challenge of standardising the Grid programming model and associated management services is still unfulfilled.

Figure 1: Initial SIMDAT Architecture SIMDAT has adopted a pragmatic approach for using existing Grid infrastructure and Web Service technologies. The application sectors faced the challenge of selecting Grid technologies that best fitted their scenarios, even if they did not provide all of the necessary functionality. Key among these are GRIA4 (open source Grid middleware developed by IT Innovation to enable commercial use of the Grid in a secure, interoperable and flexible manner), Globus,5 and J2EE6 portals. The application activities concluded that in the short-term, unless and until a standardised Grid programming model is agreed upon, new developments should be based on Web Service standards such as WS-I.7 GRIA emerged as a core technology to support collaborative work in the SIMDAT aerospace and automotive activities because of its availability, its adherence to WS-I, and its explicit support for B2B collaborations. The SIMDAT meteorology activity is developing a Data Grid based on Open Grid Services Architecture Data Access and Integration8 (OGSA-DAI) and Web Service technology, while the SIMDAT pharmaceutical activity is deploying a Web Services Grid leveraging E2E (end-to-end) security component developed during the GEMSS project.9 The initial architecture (Figure 1) shows how WS-I can provide a common API for distributed services, but it does not currently meet Grid infrastructure requirements for providing a standardised approach for managing stateful resources, as proposed by WS-RF.

SIMDAT provides application sectors with a Grid infrastructure roadmap that tracks the rapidly changing Grid landscape. During 2005, the situation has evolved significantly as GRIA continues to be developed and as technologies such as GT410 and gLite11 emerge. Following the recent delivery of the first SIMDAT prototypes, the application activities are feeding back lessons learned, which will be factored into the roadmap and into the Grid technologies. In the longer term SIMDAT aims to achieve interoperability between different Grid infrastructures such as GRIA and GT4, with a Grid service API based on WS-RF, although the level of compliance may differ between implementations.

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Reference this article
Boniface, M., Upstill, C. "SIMDAT," CTWatch Quarterly, Volume 1, Number 4, November 2005. http://www.ctwatch.org/quarterly/articles/2005/11/simdat/

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