The Application of Petri Nets to Workflow Management

1
Paper Summary (1)
/153
2
Paper Summary (2)
3
Paper Summary (3)
I forgot fairness in the previous slide. Very
important because Soundness and Fairness
Guarantee that each case will end in place o
eventually
A WF PN is sound if and only if is Live and
Bounded
PN
o
i
We know how to handle it
4
Paper Summary (4)
Sound Safe
S-Coverable PN
Sound WS FC
(iff starting from each place it is possible to
identify a subnet that is strongly connected, is
a state machine and for each place in the subnet,
each transition connected to that place belong to
the subnet)
Sound FC WS
S-C

• Always safe
• S-cov. Cheched in pol. time

• Soundess is NP-complete

WS
FC
Well-Structured PN

• A FC PN can be checked for soundness in
  polynomial time
• NFC PNs may have anomalous behaviors difficult to
  trace

Free-choice PN
(Balanced AND/OR-splits and AND/OR-joins)

• Confusion
• There are NFC PN that correspond to WF
• There are FCPN that make no sense

A WS PN can be checked for soundness in
polynomial time
5
Discussion (1)

• Why PN?
• What about FSMs?
• D. Wodtke, G. Weikum, A Formal Foundation For
  Distributed Workflow Execution Based on State
  Charts,Proc. International Conference on
  Database Theory, 1997
• Muth, P., Wodtke, D., Weissenfels, J., Weikum,
  G., Kotz Dittrich, A., Enterprise-wide Workflow
  Management based on State and Activity Charts, 
  in A. Dogac, L. Kalinichenko, T. Ozsu, A. Sheth
  (Eds.) Workflow Management Systems and
  Interoperability, Springer Verlag, 1998  

6
Discussion (1.1)

• In fact only 4 tools that constitute 1 complete
  toolset are presented that are based on PN
• Not enough to have a clear idea of whats going
  on in the real world
• The Author says that many tools are not based on
  PN. Which are the other model? Are they formal?
  Is it possible to verify the property?

7
Discussion (2)

• Othogonalization of concerns
• Computation vs. Communication
• Task vs. Resource
• What about interoperability?
• Communication between different WFP engine

8
Little demo and links

• (I had to many things to do, its all I could do)
• ExSpect (Performance Analysis) exspect.com
• Protos (Design) pallas.nl
• Woflan (verification) http//tmitwww.tm.tue.nl/res
  earch/workflow/woflan/
• http//www6.software.ibm.com/FlowMark/demo1.htm
• http//www.daimi.au.dk/PetriNets/
• http//wwwis.win.tue.nl/wsinwa/tools.html