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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

outline
Outline

1.Introduction

2. Workflow and workflow management system

3. Petri nets

4. Petri net-based workflow modeling

5. Petri net-based workflow software

introduction1
Introduction
  • 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
introduction2
Introduction
  • 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
workflow
Workflow系統特徵
  • 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
workflow1
Workflow系統特徵
  • WfMS由兩元件所組成
    • The workflow model(process definition)
    • The workflow execution module(workflow enactment service )
workflow2
Workflow型態
  • 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
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
  • INCOME
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)
slide35
GSPN
  • 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)
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