Integrated Research in GRID Computing

1. Introduction (p. 32)
The Grid vision introduced in the end of the nineties has now become a reality with the availability of quite a few Grid infrastructures, most of them experimental but some others will come soon in production. Although most of the research and development efforts have been spent in the design of Grid middleware systems, the question of how to program such large scale computing infrastructures remains open. Programming such computing infrastructures will be quite complex considering its parallel and distributed nature.

The programmer vision of a Grid infrastructure is often determined by its programming model. The level of abstraction that is proposed today is rather low, giving the vision either of a parallel machine, with a message-passing layer such as MPI, or a distributed system with a set of services, such as Web Services, to be orchestrated. Both approaches offer a very low level programming abstraction and are not really adequate, limiting the spectrum of applications that could take benefit from Grid infrastructures.

Of course such approaches may be sufficient for simple applications but a Grid infrastructure has to be generic enough to also handle complex applications with ease. To overcome this situation, it is required to propose high level abstractions to facilitate the programming of Grid infrastructures and in a longer term to be able to develop more secure and robust next generation Grid middleware systems by using these high level abstractions for their design as well. The current situation is very similar to what happened with computers in the sixties: minimalist operating systems were developed first with assembly languages before being developed, in the seventies, by languages that offer higher levels of abstraction.

Several research groups are already investigating how to design or adapt programming models that provide this required level of abstraction. Among these models, component-oriented programming models are good candidates to deal with the complexity of programming Grid infrastructures. A Grid application can be seen as a collection of components interconnected in a certain way that must be deployed on available computing resources managed by the Grid infrastructure.

Components can be reused for new Grid applications, reducing the time to build new applications. However, from our experience such models have to be combined with other programming models that are required within a Grid infrastructure. It is imaginable that a parallel program can be encapsulated within a component. Such a parallel program is based on a parallel programming model which might be for instance message-based or skeletonbased.

Moreover, a component oriented programming model can be coupled with a service oriented approach exposing some component ports as services through the use of Web Services. The results of this is that this combination of several models to design Grid applications leads to a major challenge: the deployment of applications within a Grid infrastructure.

Such programming models are always implemented through various runtime or middleware systems that have their own dependencies vis-a-vis of operating systems, making it extremely challenging to deploy applications within a heterogeneous environment, which is an intrinsic property of a Grid infrastructure.

The objective of this paper is to propose a common deployment process based on the experience gained from the ASSIST and GridCCM projects.