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Work process Description Language and Workflow Patterns

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  1. Workflow Description Language and Workflow Patterns Yi Wang

  2. Outline • What is Workflow? • Workflow Management System • Workflow Reference Models • Workflow Description Language • Workflow Patterns

  3. Workflow Definition • The automation of a business process, in whole or part. • Information or tasks are passed from one participant to another for action, according to a set of procedural rules. • A number of logical steps, each of which is known as an activity.

  4. Example of Workflow

  5. Example

  6. Workflow Management System--Definition • A system that completely defines, manages and executes “workflows” through the execution of software whose order of execution is driven by a computer representation of the workflow logic.

  7. Three function areas --Supporting WFM • The Build-time functions, concerned with defining, and possibly modeling, the workflow process and its constituent activities • The Run-time control functions concerned with managing the workflow processes in an operational environment and sequencing the various activities to be handled as part of each process • The Run-time interactions with human users and IT application tools for processing the various activity steps

  8. Types of Workflow Product • FlowMark (IBM) • Lotus Notes(IBM/Lotus) • Ad hoc • WorkMAN (Reach Software)

  9. Workflow Reference Model • A reference model for workflow management systems has been defined by the WfMC(Workflow Management Coalition). • Specify a framework for workflow systems, identifying their characteristics, functions and interfaces.

  10. WAPI • Workflow Application Programming Interface • The interface around the workflow enactment • A service interface which is to support workflow management functions across the 5 functional areas.

  11. Workflow Enactment Services • A software service • Consist of one or more workflow engines in order to create, manage and execute workflow instances. • Applications may interface to this service via the WAPI.

  12. Workflow Engine • A workflow enactment service consists of mutiple workflow engines. • A software service or "engine" • Execute environment for a workflow instance • Responsible for the part or all of the runtime control environment within an enactment service.

  13. Process and Activity State Transitions • The workflow enactment service may be considered as a state transition machine, • Individual process or activity instances change states in response to external events(eg completion of an activity) • Specific control decisions taken by a workflow engine(eg navigation to the next activity step within a process)

  14. A Basic Example

  15. Process Definition Tools • To create model, describe and document a business process. • Based on • Process definition language • Object relationship model • A set of routing commands to transfer information between participating users

  16. A Basic Meta-Model • WFMCis developing a meta-model for the process definition • Meta-Languages is a superset of constructs that is in process modeling languages

  17. Workflow Description Language • A process description, is a structure describing the tasks or activities to be executed and the order of their execution. • The process description can be provided in Workflow Description Language.

  18. Meta-Language for Workflow and Process Modeling • WPDL(Workflow Process Definition Language) • PIF(Process Interchange Framework) • PSL(Process Specification Language) • GPSG(Generalized Process Structure Grammars) • Unified Modeling Language

  19. A Business Process

  20. Workflow Process Definition Language(WPDL) • Defining the actions to be carried out in each possible state • Pre- and post-conditions of states • Transitions between states • Defining the sequencing of tasks / states • Defining automated states and states requiring user input

  21. PIF • Processes are presented at various levels of abstraction. • Object-Oriented concept of inheritance. • Hierarchy structure.

  22. PIF

  23. PSL(Process Specification Language) • To support communication between different applications based on a common understanding of their environment. • Develop a common exchange format for different modeling description.

  24. A brief summary • WPDL, PIF, PSL represent IPO-based process modeling languages. • IPO(Input-Process-Output) • IPO-based languages describe a workflow as a directed graph of activities, denoting the sequence of their execution.

  25. GPSG • Generalized Process Structure Grammars. • A constraint-based approach to process modeling.

  26. GPSG example • For IPO-based language the sequence of two activities is denoted as • B.start :=A.end • For GPSG, contain following constraints • B.start = A.end • B.end < deadline • B.start = B.end – B.average_duration

  27. Unified Modeling Language • Defines different diagram types for the design object-oriented software systems • Helps you specify, visualize, and document models. • Offers graphical notations for workflow models.

  28. Workflow Patterns • A process requires the activation of multiple tasks. • Refers to the relationship among the tasks of a process. • The workflow description languages and the mechanisms to control the enactment of a case must have provisions to support these temporal relationships.

  29. Basic workflow patterns graph

  30. Basic workflow patterns graph

  31. Reference • Internet-Based Workflow Management: Towards a Semantics Web. Dan.C.Marinescu. Wiley, 2002 • Workflow:An Introduction. Rob Allen, Open Image Systems Inc., United Kingdom Chair, WFMC External Relations Committee • Using Web Services and Workflow Ontology in Multi-Agent Systems. Jarmo Korhonen, Lasse Pajunen, and Juha Puustjärvi

  32. Reference • Workflow: An Introduction. Rob Allen, Open Image Systems Inc., United Kingdom. Chair, WfMC External Relations Committee. • Workflow Process Definition Language-Development and Directions of a Meta-Language for Workflow Processes. Michael zur Mühlen, Jörg Becker • Workflow Management Coalition The Workflow Reference Model Document Number TC00-1003 Document Status - Issue 1.1 19-Jan-95 Author:David Hollingsworth