70 likes | 216 Views
Dynamism in BPEL. Onyeka Ezenwoye Latin American Grid project. Monday, August 28, 2006. The need for Dynamism. Fault Tolerance Network failure, resource availability, etc Optimization Responsiveness to real-time events, resource scheduling, etc Variations in user input
E N D
Dynamism in BPEL Onyeka Ezenwoye Latin American Grid project. Monday, August 28, 2006
The need for Dynamism • Fault Tolerance • Network failure, resource availability, etc • Optimization • Responsiveness to real-time events, resource scheduling, etc • Variations in user input • Multiple configurations for experiments.
Approaches to dynamism(1) • Fool the System • Actions are performed outside the control of the workflow. • Workflow unaware of changes. • Usually through some middleware • Message redirection, dynamic binding • May use high-level policy • E.g. TRAP/BPEL [1]
Approaches to dynamism(2) • Modify running workflow instance • Task may be cancelled, delegated or redirected. • Other instances of the same workflow are not affected. • Usually requires some dependency list and/or policy specification • E.g. ScyFlow [2], TRIANA [3]
Approaches to dynamism(3) • Modify workflow definition • New behaviour specified in Workflow definitions. • May migrate running instances to new ones. • Migration requires careful management • Difficult to encapsulate every possible orchestration response. • Administrative overhead.
BPEL and dynamism • BPEL is NOT dynamic! • Adequate semantics (pick, skip tasks) • Hierarchical but not modular. • May implement process as several interacting workflows (cumbersome). • Minimal fault handling. • Supports compensation handling. • Dynamism through middleware • application, messaging.
References • Onyeka Ezenwoye and S. Masoud Sadjadi. Trap/bpel: A framework for dynamic adaptation of composite services. Technical Report FIU-SCIS-2006-06-02. • Karen M. McCann et. al.; ScyFlow: An Environment for the Visual Specification and Execution of Scientific Workflows. • Matthew Shields and Ian; Taylor Programming Scientific and Distributed Workflow with Triana Service. • Niels Joncheere et. al; Requirements for an Aspect Oriented Workflow system for Grid Services. • Fabio Casati; A Discussion on Approaches to Handling Exceptions in Workflows. • Rashid Hamadi et. al.; Recovery Nets: Towards Self-Adaptive Workflow Systems.