Workflow Description Language and Workflow Patterns Yi Wang

Workflow Description Language and Workflow Patterns Yi Wang

Outline n n n What is Workflow? Workflow Management System Workflow Reference Models Workflow Description Language Workflow Patterns

Workflow Definition n 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.

Example of Workflow

Example

Workflow Management System --Definition n 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.

Three function areas --Supporting WFM n n n 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

Types of Workflow Product n n Flow. Mark (IBM) Lotus Notes(IBM/Lotus) Ad hoc Work. MAN (Reach Software)

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

WAPI n n n 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.

Workflow Enactment Services n n n 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.

Workflow Engine n n 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.

Process and Activity State Transitions n n n 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)

A Basic Example

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

A Basic Meta-Model n n WFMC is developing a meta-model for the process definition Meta-Languages is a superset of constructs that is in process modeling languages

Workflow Description Language n n 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.

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

A Business Process

Workflow Process Definition Language(WPDL) n n n 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

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

PIF

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

A brief summary n n n 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.

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

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

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

Workflow Patterns n n n 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.

Basic workflow patterns graph

Basic workflow patterns graph

Reference n n n 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

Reference n n n Workflow: An Introduction. Rob Allen, Open Image Systems Inc. , United Kingdom. Chair, Wf. MC 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 TC 00 -1003 Document Status - Issue 1. 1 19 -Jan-95 Author: David Hollingsworth