Vega: A Service-Oriented Grid Workflow Management System
Because of the nature of the Grid, Grid application systems built on traditional software development techniques can only interoperate with Grid services in an ad hoc manner that requires substantial human intervention. In this paper, we introduce Vega, a
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. Because of the nature of the Grid, Grid application systems built on traditional software development techniques can only interoperate with Grid services in an ad hoc manner that requires substantial human intervention. In this paper, we introduce Vega, a pure service-oriented Grid workflow system which consists of a set of loosely coupled services co-operating each other to solve problems. In Vega, the execution flow of its services is isolated from their interactions and these interactions are explicitly modelled and can be dynamically interpreted at run-time. Keywords: Grid workflow, Service-oriented computing, Grid protocols.
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Introduction
Current Grid research intends to develop techniques for building more flexible, autonomous and adaptive Grid systems [1]. For this purpose, all the participant services are required to interoperate in a highly flexible and dynamic way. Firstly, Grid services should agree on the transport protocols and on the message structure and format in advance. Secondly, service providers should be able to specify their particular interaction protocols, that is, the expected sequence of messages for providing their services and, on the other hand, service consumers should be able to obtain those specifications and to dynamically interpret them. The agreement on the transport protocols was proposed in [2] and based on these foundations, the Open Grid Service Architecture (OGSA) [3] was developed. More recently, the Web Service Resource Framework (WSRF) [4] was proposed for the management and the access to the state of Grid services. Nonetheless, despite the homogeneous mechanisms defined by WSRF, each WSRF-compliant provider assumes its own and exclusive interaction requirements and this heterogeneity in the interactions among Grid services may introduce a barrier to interoperability.
This work has been supported by the research project PIP086/2005, granted by the Government of Arag´ on and the project TIN2006-13301, granted by the Spanish Ministry of Education and Science.
R. Meersman and Z. Tari et al. (Eds.): OTM 2007, Part II, LNCS 4804, pp. 1516–1523, 2007. c Springer-Verlag Berlin Heidelberg 2007
Vega: A Service-Oriented Grid Workflow Management System
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Fig. 1. DENEB in execution
In general terms, application systems and, in particular, Grid workflow systems should be designed to overcome this barrier. At the time that a candidate Grid service is chosen and the user-specified task is due to be executed, service consumers should be provided with a way of interacting with the candidate service without requiring to re-compile its software. This could be accomplished by explicitly separating the process flow of services and their interactions and dynamically interpreting the interactions [5,6]. Nevertheless, current Grid workflow management projects [7], which have had great success at different application scenarios and which offer different approaches for building and executing workflows on Grids, do not overcome this barrier to interoperability successfully. In this paper, we intro
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