WorkFlow Modeling based on Petri-nets Approach

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WorkFlow Modeling based on Petri-nets Approach

• Lee Hyoung Gon
• 2000.8.10

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On the automatic generation of workflow processes
based on product structures

• W.M.P van der Aalst
• Department of Mathematics and Computing Science,
• Eindhoven University of Technology, Netherlands
• Accepted 11 December 1998, Computers in
  Industry

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Abstract

• WFMS are case-driven in the sense that tasks are
  executed for specific cases.
• A case corresponds to a product that needs to be
  produced.
• Therefore, the well-known BOM can be used to
  describe the product that is manufactured using a
  WFMS.
• end-product view of workflow design,
  constitute a basis for the automatic
  configuration of s WFMS

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Administrative Processes vs Production Processes

• Similarities
• Focus on the routing of work, allocation of work
  to resources.
• Performance indicators(throughput time, waiting
  time, service level, utilization)
• Differences
• Products physical objects/informational
• Making a copy is easy, no limitations on
  in-process inventory, less requirements for
  order, quality is difficult to measure,
  transportation of electronic data is timeless,
  production to stock is seldom possible
• Not so much methods, techiques and tools have
  been developed.(like BOM or MRP,TQM,OPT,JIT,EOQ)

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WFMS in a historical perspective

• However, the process is not a goal by itself. It
  is important to define the output of the workflow
  process.

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BOM of an cases- product centric view

• variant BOM we extend the classical BOM with
  options(? or not) and choices(O).(Quantity
  1, each component appears only once in the BOM.)

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About Petri nets

• The classical Petri net was invented by Petri in
  the sixties.
• In the last two decades, the classical Petri net
  has been extended with color, time and hierarchy.
• Several reasons for using Petri nets
• Formal semantics, Graphical nature,
  Expressiveness, Properties, Analysis,
  Vendor-independent
• A Petri net is a tuple (P, T, F)
• - P is a finite set of places
• - T is a finite set of transitions (P?T?)
• - F?(P?T)?(T?P) is a set of arcs (flow
  relation)

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Petri nets Workflow processes modeling-
process centric view
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Mapping the BOM onto Petri nets(1/3)
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Mapping the BOM onto Petri nets(2/3)- Mapping
Algorithms
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Mapping the BOM onto Petri nets(3/3)- two level
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Extensions - Precedence constraints
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Extensions Grouping Iteration

• Grouping
• The execution of one task may lead to the
  production of several products.
• Iteration
• This information can be added to the BOM by
  indicating that certain components may require
  multiple production steps.
• Etc
• Modular BOM(reuse), generic BOM(inheritance),
  comparative BOM(overiding)

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Generic BOM adaptive workflow

• Product configuration
• Ex) Car X, which may have
• 16 possible colors, 5 possible engines, 10
  options 81,920 variants.
• gt instead of defining 81,920 different BOM, one
  generic BOM is defined.
• Todays WFMSs are ill-suited to dealing with
  change.
• Ad-hoc changes
• Evolutionary changes

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Conclusion

• We have assumed that the process is generated on
  the basis of a BOM.
• In many situations, this is not very realistic
  both the product-centric view and the
  process-centric view are useful.
• In our opinion, the validation of the workflow
  process by comparing it with the BOM is an
  important topic for the further research.

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Formalization and verification of event-driven
process chain(EPCs)

• W.M.P van der Aalst
• Department of Mathematics and Computing Science,
• Eindhoven University of Technology, Netherlands
• Accepted 4 March 1999, Information And Software
  Technology

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Abstract

• Some of the leading product(R/3, ARIS) use EPCS
  to model business processes.
• Although the EPCs have become a widespread
  process modeling techinique, they suffer from a
  serious drawback niether the syntax nor the
  semantics of an EPC are well defined.
• It is shown that the correctness of an EPC can be
  checked in polynomial time by using
  Petri-net-based analysis techniques.

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Mapping EPCs onto Petri net.
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Loosely coupled interorganizational
workflowsmodeling and analyzing workflows
crossing organizational boundaries

• W.M.P van der Aalst
• Department of Mathematics and Computing Science,
• Eindhoven University of Technology, Netherlands
• Accepted 24 July 1999

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interorganizational loosely coupled

• Technologies such as EDI, WWW, EC, virtual
  organizations, extended enterprises highlights
  the fact that more and more business processes
  are crossing organizational boundaries.
• Loosely coupled each partner takes care of a
  specified part of the process.(but have to
  synchronize at certain points to ensure the
  correct execution of the overall business
  process.)
• cf) capacity sharing, chained execution,
  subcontracting, case transfer

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Two Questions

• (1) what are the minimal requirements any
  interorganizational workflow should satisfy?
• (2) how does one decide whether an
  interorganizational workflow, modeled in terms of
  Petri nets, is consistent with an interaction
  structure specified through a message sequence
  chart?

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An example of interorganizational workflow

• An example of interorganizational workflow

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Verification

• Soundness
• For any case, the procedure will terminate
  eventually and the moment the procedure
  terminates, there is a token in the output place
  and all the other planes are empty.
• There should be no dead tasks.
• An interorganizational workflow is locally sound
  if and onlyif each of the local WF-nets in
  isolation is sound.
• An interorganizational workflow is globally sound
  if the extended net is sound.
• Woflan verifying soundness tool.(liveness,
  boundedness)
• ltwe need to prove soundeness for n1
  WF-nets(n local WF-nets and the extended net).gt

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Verification

• Consistency
• An interorganizational workflow is consistent
  with respect to an MSC if all possible firing
  suquences satisfy the partial order specified by
  the MFC.
• Instead of checking all possible firing
  suquences, we use a technique based on a
  generalization of the notion of implicit places.

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Reference

• On the automatic generation of workflow processes
  based on product structures, Computers in
  Industry, Volume 39, Issue 2, July 1999, Pages
  97-111
• Formalization and verification of event-driven
  process chains, Information and Software
  Technology, Volume 41, Issue 10, 15 July 1999,
  Pages 639-650
• Loosely coupled interorganizational workflows
  modeling and analyzing workflows crossing
  organizational boundaries, Information
  Management, Volume 37, Issue 2, 1 March 2000,
  Pages 67-75
• Liveness, fairness, and recurrence in Petri nets,
  Information Processing Letters, Volume 70, Issue
  6, 30 June 1999, Pages 269-274 Ekkart Kindler
  and Wil van der Aalst
• Verification of Workflow Task Structures A
  Petri-Net-Based Approach, Information Systems,
  Volume 25, Issue 1, 2000, Pages 43-69
• Process-Oriented Architectures for Electronic
  Commerce and Interorganizational Workflow,
  Information Systems, Volume 24, Issue 8, December
  1999, Pages 639-671

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My Conclusion

• Petri net? workflow? ????? ????, ????? ????? ??
  ????.
• ????? ??? ????? Workflow? ???? ??? ?? ??? ???????
  ??? ?? ???? ?????? ERP? ?????? ? ????
• Workflow? ?? ????? WFMS? ?????, ?? ?????
  Workflow? ??? ?? ????? ??? ???? ? ??? ??? ???.