Keywords: grid technology, open grid service architecture, distributed systems, distributed abstract state machine, web services, formal models.

Among OGSA services it is particularly critical that the job management and execution capability of a grid, which concerns searching candidate locations and executing and managing jobs until the end. Such a functionality enables users to use distributed resources for their applications, even if in a non-uniform and standard way. These tasks are critical in the grid system context because their incorrect execution can heavily affect provided services, so adoption of formal method is sometimes mandatory.

This paper is aimed at defining an abstract model for specifying the job management and execution services. We propose as formal model a distributed abstract state machine (DASM) [2] to analyse and design of the OGSA capability: it constitutes an abstract interpreter for the grid standard system. The adoption of ASM helps different grid middlewares to be studied in the same way, finally achieving also interoperability and standardization. We capture capability properties and have generated ASM ground model. We formalize it in the ASM rules of the activities, and we analyse research problems using an appropriate abstraction level, including abstract instructions for changing state.

Starting from a ground model of job management and execution service, we build a DASM model for the grid service. An implementation has been developed with the coreASM toolkit [3], that performs a graphical model for design and validation as well as verification of the ASM.

This approach is able to describe components of a grid system, dynamical properties and relations between them in a service-oriented view, that can be abstracted or refined as the designer needs, based on environment specifications. Different grid strategies, depending on different middleware, can be derived as different refinements of the same abstraction. Furthermore, this approach allows us to isolate and to concentrate on the essential parts of the grid system for refinement.

A ground model to fully capture the informal requirements in a mathematically verifiable code has been constructed. We have presented an implementation, developed with the coreASM toolkit.

In the future, we will analyse in detail some grid aspects through ASM refinement, and we will make efforts to construct grid models with user requirements such as performance metrics. We will attempt to complete the architectural specification model in which all the desired properties of grids are addressed.

1

I. Foster, I. Kishimoto, H. Savva, A. Berry, D. Djaoui, A. Grimshaw, A. Horn, B. Maciel, F. Siebenlist, F. Subramaniam, R. Treadwell, J. Reich, J.V. Reich, "The Open grid Services Architecture, Version 1.5" , GFD-I.080, Open grid Forum, 2006.

2

E. Börger, R. Stärk, "Abstract State Machine", Springer, 2003.

3

http://www.coreasm.org/

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