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Techniques for Modeling Workflows and Their Support of Reuse. 第 2 組 組員 : 9634516 Kent 倪煒均 9634532 Ashley 黃雅莉 9634543 Dragon 郭奇龍 2007/10/11. Abstract.

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Techniques for modeling workflows and their support of reuse

Techniques for Modeling Workflows and Their Support of Reuse




9634532 Ashley 黃雅莉




  • Several authors propose their own technique based on Petri Nets to model workflow processes. But suggest totally different solutions.

  • Because the proposed techniques and fundamentally different, eleven of these techniques are briefly discussed and compared

What is workflow
What is workflow?

  • The automation of a business process, in whole or part, during which documents, information or tasks are passed from one participant to another for action, according to a set of procedural rules.

Definition of basic workflow
Definition of Basic Workflow

  • Workflow Management Coalition (WEMC): provides a common “Reference Model” of workflow management systems to identify workflow management system’s characteristics, terminology and components.

  • Workflow management system is a software system that defines, coordinates, manages, and executes complex business activities.

Van der Aalst (1996)

-formal semantics despite their

graphical nature-can explicitly model states -have abundance of available and

theoretically proven analysis


  • Oberweis et al (1997)

  • -Integration of data and behaviour

  • aspects.-Support for concurrent, cooperative

  • processes.-Different degrees of formality-Availability of analysis techniques-Flexibility

Why Petri Nets to Model Workflow?

Merz. Et al (1995)

-mathematical foundation

-graphical representation


High level petri nets
High Level Petri Nets

  • Information Control Nets (ICN) adding a complementary data flow model, generalising control flow primitives and simplifying semantics

  • Coloured Petri Nets in order to enhance the distributed systems architecture Common Open Service Market (COSM), with concurrent workflow modeling.

  • Reconfigurable Netsconsists in fact of several Petri Nets which constitute the different possible configurations of the system.


  • First introduced by Carl Adam Petri in 1962.

  • A diagrammatic tool to model concurrency and synchronization in distributed systems.

  • Very similar to State Transition Diagrams.

  • Used as a visual communication aid to model the system behaviour.

  • Based on strong mathematical foundation.

A petri net specification
A Petri Net Specification ...

  • consists of three types of components: places (circles), transitions (rectangles) and arcs (arrows):

    • Places represent possible states of the system;

    • Transitions are events or actions which cause the change of state; And

    • Every arc simply connects a place with a transition or a transition with a place.

A change of state
A Change of State …

  • is denoted by a movement of token(s) (black dots) from place(s) to place(s); and is caused by the firing of a transition.

  • The firing represents an occurrence of the event or an action taken.

  • The firing is subject to the input conditions, denoted by token availability.

A change of state1
A Change of State

  • A transition is firable or enabled when there are sufficient tokens in its input places.

  • After firing, tokens will be transferred from the input places (old state) to the output places, denoting the new state.

  • Note that the EFTPOS example is a Petri net representation of a finite state machine (FSM).

Net structures









Net Structures

  • A sequence of events/actions:

  • Concurrent executions:

Net structures1





Net Structures

  • Non-deterministic events - conflict, choice or decision: A choice of either e1, e2 … or e3, e4 ...

Net structures2


Net Structures

  • Synchronization

Net structures3


Net Structures

  • Synchronization and Concurrency

Stochastic petri nets
Stochastic Petri Nets

  • GSPN (Generalized Stochastic Petri Nets)

    1.Quantitative analysis

    2.Qualitative analysis

  • CGSPN (the Coloured Generalized Stochastic Petri Nets)– which are based on Coloured Petri Nets as pure Petri Net formalism instead of Place/Transition Petri Nets.

Behavioural properties
Behavioural Properties

  • Reachability

    • “Can we reach one particular state from another?”

  • Boundedness

    • “Will a storage place overflow?”

  • Liveness

    • “Will the system die in a particular state?”

Other types of petri nets
Other Types of Petri Nets

  • High-level Petri nets

    • Tokens have “colours”, holding complex information.

  • Timed Petri nets

    • Time delays associated with transitions and/or places.

    • Fixed delays or interval delays.

    • Stochastic Petri nets: exponentially distributed random variables as delays.

Other types of petri nets1
Other Types of Petri Nets

  • Object-Oriented Petri nets

    • Tokens are instances of classes, moving from one place to another, calling methods and changing attributes.

    • Net structure models the inner behaviour of objects.

    • The purpose is to use object-oriented constructs to structure and build the system.

An o o petri net













data: ITEM

data: ITEM

ITEM produce( )

ITEM accept( )

void send(ITEM)

void consume(ITEM)

An O-O Petri Net

Application generators and very high level languages
Application Generators and Very High-Level Languages

  • Allow users to specify the requirements at a very high level of abstraction.

  • In the long term, it would have the highest potential profit. However, it remains very difficult to build generators that scale up to industrial production


  • Most common approach black-box reuse

  • The notion of compositionality

  • Questions(which advantages exactly can be achieved or which type of reuse leads to these advantages)remains unanswered

A critical remark concerning reuse in the is literature
A Critical Remark Concerning Reuse in the IS-Literature

  • It has remained extremely difficult to realize a systematic approach to reuse.

  • The potential reasons for the lack of systematic reuse:some technical but many are managerial

Hidden assumptions
Hidden Assumptions

  • A fundamental problem of software

  • Intended environment


    (2)don’t match the actual environment or

    (3)conflict with those of other parts of the system

Final remarks
Final Remarks

  • Realizing a systematic form of reuse has proven to be a very ambitious goal ---To reach this goal ,good modeling constructs alone have been insufficient

  • Making quick progress towards deciding which modeling constructs are most appropriate

  • Empirical and experimental studies are required(have yet find in the literature)


  • Identify the existing Patri Net formalisms proposed by various authors

  • Is that even a very good Petri Net formalism for modeling workflows is not worth much if there are no Workflow Management Systems or other computer based on it?

  • V.S database models:far from being mature

Conclusion con

  • Much progress is being made towards developing an adequate modeling construct for modeling workflows using Patri Nets

  • Construct alone isn’t sufficient in IS-field, and how’s in workflow field?