Petri net based modelling of workflow system an overview
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Petri net-based modelling of workflow system : An overview. Professor : Dr. Ou-Yang Reporter :陳星豪 李高樺 洪淨池 魏廷璋. Outline. 1.Introduction 2. Workflow and workflow management system 3. Petri nets 4. Petri net-based workflow modeling 5. Petri net-based workflow software. Introduction.

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Petri net based modelling of workflow system an overview

Petri net-based modelling of workflow system:An overview

Professor:Dr. Ou-Yang

Reporter:陳星豪 李高樺

洪淨池 魏廷璋



2. Workflow and workflow management system

3. Petri nets

4. Petri net-based workflow modeling

5. Petri net-based workflow software


  • The core of workflow system is the notion of business process, which is a set of activities with a common goal

  • Workflow符合企業先前定義的需求,支援執行一連串需要使用人力以及各種資源的活動


  • Petri nets are applied in different discrete-event dynamic systems, which are characterised by parallelism and synchronization

  • Petri nets-based modelling and analysis of workflow and workflow system is an active research area in academic

  • A small number of vendor have developed Petri nets-based workflow management system (WfMS)

Workflow and workflow management system1
Workflow and workflow management system

  • 1970年代,workflow的概念從工廠自動化的觀念中延伸而出,第一個workflow的雛形被發展出來

  • 1970~1980年間,Backtalk、Office Talk-P、Office Information System是最早發行的workflow系統雛形

  • 1980年代晚期開始,WfMS和ㄧ些computer-based system進行結合,例如:DBMS、document imaging或e-mail


  • 一個workflow本身就是一個流程,使文件、資訊或工作在一個與多個參與者之間傳遞,共同協調執行,涵蓋到組織之間與內部的資訊流和控制流

  • Workflow Management Coalition

    • A Workflow as a computerised-based facilitation or automation of business process, in whole or part

  • A specific software system, WfMS, manages and executes workflow through the execution of software whose order of execution is driven by a computer representation of the workflow logic


  • WfMS由兩元件所組成

    • The workflow model(process definition)

    • The workflow execution module(workflow enactment service )


  • 以流程定義與工作派工來看,有三種型態workflow

    • Production workflow

      • 固定的工作定義與執行次序

    • Administrative workflow

      • Cases 大致遵循原本已定義完成的程序,但是有另一條途徑供選擇

    • Ad hoc workflow

      • 以事先定義的流程樣版來驅動cases進行

      • 流程樣版能被修正以符合某些特定cases的需求

Petri nets1
Petri nets

  • 一種modelling工具,由Petri所建構

  • 圖形化概念具有自我文件化(self-documenting)的能力,成為從事設計流程的有力工具

  • 建立數學模式來描述系統的行為

  • 驗證模式

  • 適用於離散事件動態系統(discrete event dynamic systems)的modelling與分析,具有平行與同步作業的特性

Petri nets2
Petri nets

  • Three structural components

    • Places

    • Transitions

    • Arcs

  • Places以圓圈表示,代表系統的狀態與條件

  • Transitions以長柱形或長盒形表示,描述可能改變系統狀態的事件

  • Places與Transitions之間的關係以單一方向之Arcs連結

  • 兩個相同型態的節點之間不能相互連結

  • 系統的動態行為可以用tokens來呈現

Petri nets3
Petri nets

  • Petri nets的正式定義為

    • A Petri net is a 4-tuple N = {P, T, F, M0}

M which represents a state of the modelled system is a distribution of tokens over the set of places

Petri nets4
Petri nets

  • Two classes of properties of Petri net-based model system

    • Behavioural or marking dependent properties

      • Depending on the initial marking of the model

    • Structural properties

      • Relate to the structure of the modeled system and independent of the initial marking

Petri net based workflow modeling

Petri net-based workflow modeling

Workflow modelling
Workflow modelling

  • It is criticized that they have

    • no needed functionality

    • no clear set of definition

    • no general conceptual model

Petri net based workflow modeling1
Petri net-based workflow modeling

  • Zismann第一次應用Petri nets在辦公室流程上,為workflow系統的早期想法

  • Ellis延伸Zismann,推出Information Control Net (ICN),並且應用在辦公室資訊系統的建構

  • Vander Aalst已經證實workflow可以與Petri net完全結合

  • Vander Aalst提出workflow有三種不同的維度:process、case以及resource

Petri net based workflow modeling2
Petri net-based workflow modeling

  • 每一個workflow的工作由transition呈現

  • Places則是描繪出一個需執行任務之pre-condition與post-condition,或是所需的資源

  • 弧線表達出任務之間的邏輯關係以及它的流向

  • Example

Resource modeling of workflow
Resource modeling of workflow

  • 前ㄧ模式只是描繪出一個workflow流程的單一instance,沒有討論到時間或資源的觀點

  • 實際的情況下,每一個流程可能需要執行超過一個以上的instance

  • Example

Petri net based workflow software1
Petri net-based workflow software

  • Protos

    • to export the processes modeled with Protos into some WfMS products such as COSA and FLOWer

  • Structware

    • a tool that allows the designer to design and simulate business processes based on Petri net models.

Petri net based workflow software2
Petri net-based workflow software

  • ExSpect

    • a business process modeling tool, able to model and analyze workflow processes in terms of Petri nets

  • Woflan

    • interfaces with the other commercial workflow products such as COSA , Staffware and Protos


Modelling and qualitative analysis of workflow
Modelling and qualitative analysis of workflow

  • qualitative analysis

    • deadlock freeness

    • the correct flow of the work

    • absence of overflow

    • the presence of certain mutual exclusion wherever shared resource are used

  • mainly concentrated on structural modelling and analysis of the qualitative properties of workflow processes

Temporal constraint petri net tcpn
Temporal Constraint Petri Net(TCPN)

  • a modified version of an ordinary Petri net

  • has been used to model workflow application at conceptual level and as a test-bed to verify the system properties.

  • Each task is decomposed into some primitives and therefore the states between the primitives can be represented. Task dependencies are categorized into control-flow dependency, value dependency and external dependency

Business procedure net bp net
Business Procedure net (BP-net)

  • Free software

  • It is proposed for representation, validation and verification business processes.

  • Then this model has been modified into a workflow net (WF-net) as a sound model for workflow

  • In order to obtain a strong sound workflow model, he has added 1-safe property to WF-net

Workflow authorization model
Workflow Authorization Model

  • This model ensures that in a workflow system, authorized resources are granted privileges on required tasks only while the task is being executed

Inter organizational workflow
Inter-Organizational Workflow

  • Inter-organizational workflow and the availability of the Internet have affect workflow technology

  • SGML

    • A Petri net structure as a base layer

    • can be used in a distributed environment

  • CPN-based Colored Petri-Net

Workflow fragmentation
Workflow Fragmentation

  • Ad hoc changes

    • related to rare events

  • Radical changes

  • Evolutionary changes

    • are often the outcomes of reengineering the system

Object oriented modeling
Object Oriented Modeling

  • Modular Process Nets

  • Higher-Order Object Net (HOON)

  • Business Process Petri nets (BPP-nets)


  • The one that mostly has been used

  • Continuous Time Markov Chain

    • Time

    • Conversion

Petri nets5
Petri nets

  • OCPN(Object Composition Petri nets)

  • XOCPN (eXtended Object Composition Petri Net)

  • DOCPN (Distributed Object Composition Petri Net)

  • TSPN (Time Stream Petri Net)