Workflow Description Language and Workflow Patterns

Yi Wang

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

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.

Example of Workflow

Example

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.

Three function areas --Supporting WFM

he 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 FlowMark (IBM) Lotus Notes(IBM/Lotus) Ad hoc WorkMAN (Reach Software)

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.

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.

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.

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.

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)

A Basic Example

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

A Basic Meta-Model 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 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 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) 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 Processes are presented at various

levels of abstraction.

Object-Oriented concept of inheritance.

Hierarchy structure.

PIF

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.

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.

GPSG Generalized Process Structure Grammars.

A constraint-based approach to process modeling.

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

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.

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.

Basic workflow patterns graph

Basic workflow patterns graph

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

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