Unpredictable job execution environments pose a significant barrier to the widespread adoption of the Grid paradigm, because of the innate risk of jobs failing to execute at the time specified by the user. We demonstrate that predictability can be enhanced with a supporting infrastructure consisting of three parts: Performance modelling and monitoring, scheduling which exploits application structure and an advanced reservation resource management service. We prove theoretically that execution times using advanced reservations display less variance than those without. We also show that the costs of advanced reservations can be reduced by providing the system with more accurate performance models. Following the theoretical discussion, we describe the implementation of a fully functional workflow enactment framework that supports advanced reservations and performance modelling thereby providing predictable execution behavior. We further provide experimental results confirming our theoretical models.

The move towards Service Grids, where services are composed to meet the requirements of a user community within constraints specified by the resource provider, present many challenges to service provision and description. To support our research activities in the autonomous composition of services to form a Semantic Service Grid we describe the adoption within ICENI of web services to enable interoperability with the recently proposed Open Grid Services Architecture.

Effective exploitation of computational grids can only be achieved when applications are fully integrated with the grid middleware and the underlying computational resources. Fundamental to this exploitation is information. Information about the structure and behaviour of the application, the capability of the computational and networking resources, and the availability and access to these resources by an individual, a group or an organisation. This paper describes an integrated grid environment that is open, extensible and platform independent. We match a high-level application specification, defined as a network of components, to an optimal combination of the currently available component implementations within our grid environment. We demonstrate the effectiveness of this architecture through high-level specification and solution of a set of linear equations by automatic and optimal resource and implementation selection.