Difference: WorkflowManagementSystem (4 vs. 5)

Revision 52007-12-20 - SimonePellegrini

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Workflow Management System

The Workflow Management System (WfMS) project is developed within the CoreGRID

european project. The main goal of this project is to provide an effective solution to run complex scientific workflows modeled with Petri Nets taking full advantage of the distributed and etherogeneous nature of the Grid. One of the design principle is the neutrality towards the underlying mechanism for task execution, in order not to compromise interoperability with multiple infrastuctures.

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The fist prototype of the system have been tested with workflows accessing resources available on the Grid provided by the EGEE project, a large and relatively mature infrastucture. In particular, the execution of Grid jobs is performed by relying on the gLite Workload Management System (WMS) through its Web Service interface (WMProxy).

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Contacts

INFN Cnaf Bologna: Simone Pellegrini, Francesco Giacomini

Papers

CGW07: Simone Pellegrini, Francesco Giacomini, Antonia Ghiselli: A Practical Approach for a Workflow Management System. In Proceedings of the CoreGRID Workshop 2007, Dresden, 2007.

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ICGW08 [under reviewing process]: Simone Pellegrini, Andreas Hoheisel, Francesco Giacomini, Antonia Ghiselli: Using GWorkflowDL for Middleware-Independent Modeling and Enactment of Workflows. Submitted for the CoreGRID Integration Workshop 2008, Creta, 2008.
WSES08 [under reviewing process]: Simone Pellegrini, Francesco Giacomini: Desing of a Petri Net-based Workflow Engine. Submitted for the 3rd International Workshop on Workflow Systems in e-Science, Lyon, 2008.

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Concepts

Petri Nets in workflow modeling

Recent studies have demostrated that the modling capabilities of Petri Nets outperforms other formalisms tanks to the following properties:

the formal semantics despite the graphical nature,

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< The swOperation allows to invoke sub-workflows, which implements the particular operation. In this case, the JobExecute workflow describe (using the Petri Nets formalism) the operation to perform in order to execute a task in the gLite Grid middleware. The sequence of operation is depicted in the following figure:

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> The swOperation allows to invoke sub-workflows. A sub-workflow implements a particular operation on a specific infrastucure. In this case, the JobExecute workflow describes (using the Petri Nets formalism) the operation to perform in order to execute a task in the gLite Grid middleware. The sequence of operation is depicted in the following figure:

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and the wait_for_termination transition also invoke a sub-workflow which can be expressed (using a polling strategy) in the following figure:

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> The JobRegister, JobSubmit operations are provided by the WMS via its Web Service interface, this make it possible to express the JobExecute sub-workflow in terms of atomic operations (actually Web Service invocation) the engine can understand and execute. The execution of a job in the gLite middleware consists in a jobSubmit (which semantics can be also obtained by invoking -- in sequence -- jobRegister and a jobStart) and the monitor of the job activity until done. Job monitoring can be done via the WMS using the Logging and Bookkeeping Service (LB) also available via a Web Service interface. The wait_for_termination task can be modelled using a sub-workflow which implement a specific monitoring strategy (polling or notification-based).

Workflow Engine

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< The main component of the WfMS is the workflow engine. It is based on an semplification of the HLPN formalism.

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> The engine, represent the core component of the WfMS. It is based on the HLPN formalism and has the responsability to schedule workflow tasks accoring to their interdependencies keeping the overall state of the workflow execution. The engine deals with the non-determinism in Petri Nets providing an unique design capable of guarantee state consistency and ideally inifinite parallelism in task execution.

-- SimonePellegrini - 19 Dec 2007

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