Workflow Description Language
and Workflow Patterns
Yi Wang
Outline
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What is Workflow?
Workflow Management System
Workflow Reference Models
Workflow Description Language
Workflow Patterns
Workflow Definition
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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
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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
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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
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FlowMark (IBM)
Lotus Notes(IBM/Lotus)
Ad hoc
WorkMAN (Reach Software)
Workflow Reference Model
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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
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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
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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
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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
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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
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To create model, describe and document a
business process.
Based on
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Process definition language
Object relationship model
A set of routing commands to transfer
information between participating users
A Basic Meta-Model
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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
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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
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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)
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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
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Processes are presented at various
levels of abstraction.
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Object-Oriented concept of inheritance.
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Hierarchy structure.
PIF
PSL(Process Specification
Language)
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To support communication between
different applications based on a common
understanding of their environment.
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Develop a common exchange format for
different modeling description.
A brief summary
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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
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Generalized Process Structure Grammars.
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A constraint-based approach to process
modeling.
GPSG example
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For IPO-based language the sequence of two
activities is denoted as
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B.start :=A.end
For GPSG, contain following constraints
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B.start = A.end
B.end < deadline
B.start = B.end – B.average_duration
Unified Modeling Language
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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
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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
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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
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Workflow: An Introduction. Rob Allen, Open
Image Systems Inc., United Kingdom. Chair,
WfMC External Relations Committee.
Workflow Process Definition LanguageDevelopment 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