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Abstract-We present the ASKALON environment whose goal is to simplify the development and execution of workflow applications on the Grid. ASKALON is centered around a set of high-level services for transparent and effective Grid access, including a Scheduler for optimized mapping of workflows onto the Grid, an Enactment Engine for reliable application execution, a Resource Manager covering both computers and application components, and a Performance Prediction service based on training phase and statistical methods. A sophisticated XMLbased programming interface that shields the user from the Grid middleware details allows the high-level composition of workflow applications. ASKALON is used to develop and port scientific applications as workflows in the Austrian Grid project. We present experimental results using two real-world scientific applications to demonstrate the effectiveness of our approach.

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Advance reservation of Grid resources can play a key role in enabling Grid middleware to deliver on-demand resource provision with significantly improved Quality-of-Service (QoS). However, in the Grid, advance reservation has been largely ignored due to the dynamic Grid behavior, underutilization concerns, multi-constrained applications, and lack of support for agreement enforcement. These issues force the Grid middleware to make resource allocations at runtime with reduced QoS. To remedy these, we introduce a new, 3-layered negotiation protocol for advance reservation of the Grid resources. We model resource allocation as an on-line strip packing problem and introduce a new mechanism that optimizes resource utilization and QoS constraints while generating the contention-free solutions. The mechanism supports open reservations to deal with the dynamic Grid and provides a practical solution for agreement enforcement. We have implemented a prototype and performed experiments to demonstrate the effectiveness of our approach.

With the increasing demand for wireless packet data services, thirdgeneration (3G)