Petri Net Markup Language (PNML)

1. Petri Net Markup Language(PNML) Nickolas Paladino Oct. 9, 2002 University of Central Florida

2. Outline • PNML History • Considerations for Standard • Specification • Example Petri Net • Sample PNML

3. Outline • Application • Deficiencies • Current State • Future Direction • Conclusion • References

4. PNML History • Petri Net Tools - variety e.g. Artifex, CPN-AMI, HiQPN-Tool, Renew, PACE • Each has unique internal representation and saved/exported file format definition

5. PNML History • Reasons to move to a standard - Useful to move Net Models from tool to tool, not redesign from scratch - Make available libraries or toolkits of predefined Petri Net pieces - Moving project to different tool obsolete tool, stronger analysis, better graphics capability

6. PNML History • Obstacles to a standard - Additional development by tool designers - don’t want to loose advanced features specific to any tool - problems with extensibility e.g. Java – Sun vs Microsoft, HTML – Netscape vs Microsoft

7. Considerations for Standard • Standard should be: - simple - include only necessary technology • Reference parsers should be available • Need converters from old formats • Experience from tool developers

8. Considerations for Standard • Why XML (Extensible Mark-up Language)? - able to use robust parsers - large choice of XML tools - flexible, for easy extension of formats - parsers can ignore unknown parts

9. Specification • ISO 15909 High-level Petri Nets – Concepts, Definitions and Graphical Notation Final Draft Version 4.7.1 October 28, 2000

10. Sample Petri Net

11. Sample PNML • Sytle Sheet CSS Syntax place { shape: ellipse; } place name { font-size 12pt; } transition { shape : box } transition name { font-size: 11pt; }

12. Sample PNML • Entities extended with class information <place id="input" class="material-flow"> <name>Input</name> <type>InItem</type> </place> <arc id="a1"> <placeend idref="input" class="material-flow"> <transend idref="get-next-item"> </arc> <transition id="get-next-item" class="material-flow"> <name>Get Next Item</name> </transition>

13. Sample PNML • Petri Net mathematical description <place id="idle"> <name>Idle</name> <type>M</type> <initmark>M</initmark> </place> <arc id="a2"> <placeend idref="idle"> <transend idref="get-next-item"> <expr>m</expr> </arc> ... </pn> <pn> <place id="input"> <name>Input</name> <type>InItem</type> </place> <arc id="a1"> <placeend idref="input"> <transend idref="get-next-item"> <expr>iitem</expr> </arc> <transition id="get-next-item"> <name>Get Next Item</name> </transition>

14. Sample PNML • Petri Net layout description <node ref="machine.pn#idle"> <coord> <x>20.0</x> <y>20.0</y> </coord> </node> <conn ref="machine.pn#a2"> <coord> <x>20.0</x> <y>10.0</y> </coord> </conn> ... </layout> <layout> <node ref="machine.pn#input"> <coord> <x>10.0</x> <y>0.0</y> </coord> </node> <conn ref="machine.pn#a1"> <!-- no bend points --> <node ref="machine.pn#get-next-item"> <coord> <x>10.0</x> <y>10.0</y> </coord> </node>

15. Application • Must communicate adequate detail of Petri Net Definition Hold meaning of common notations Extend for special features of varied tools • Allows Petri Net use on different tools Varied strengths and weaknesses of tools e.g. initial design, simulation, editing, analysis, GUI

16. Deficiencies • Petri Nets graphical in nature Difficult to capture same look across existing applications • Petri Nets can become very large • Many existing Petri Net tools Retrofit of each can be time consuming and has cost Converters from old standards needed

17. Current State • The Petri Net Interchange Format Mailing List http://www.informatik.hu-berlin.de/top/PNX/ Little activity One comment since 2000 • Some tools have moved to XML-based file format

18. Future Direction • Should not force developers to use PNML • Standards committee to make format freely available • Current tools could begin to use own XML, converge to PNML

19. Conclusion • Correct direction to pursue • Needed by academia and industry • Will eventually be adopted • No technical problems in XML based PNML definitions • Agree on standard and move to implement

20. References • [Mai00] Mailund, Thomas (2000). Seperation of Style and Content with XML in an Interchange Format for High-level Petri Nets (Mailund, T. , Mortensen, K. H.),   Position Paper, 21st International Conference on Application and Theory of Petri Nets Aarhus (2000) • [Kum00] Kummer, Olaf (2000). XML and Petri Nets – Following the Forces (Kummer, O., Wienberg, F., Moldt, D.),  Position Paper, 21st International Conference on Application and Theory of Petri Nets Aarhus (2000) • [Mat00] Matthias, Jungel (2000). Towards a Generic Interchange Format for Petri Nets (Matthias, J., Kindler, E., Weber, M.),  Position Paper, 21st International Conference on Application and Theory of Petri Nets Aarhus (2000)

21. References (WWW) • The PNK Team: Petri Net Markup Language. http://www.informatic.hu-berlin.ed/top/pnml/. Aug. 2002. • Petri Net Tools and Software. http://www.daimi.aau.dk/PetriNets/tools/. Oct. 2002. • 21st International Conference on Application and Theory of Petri Nets. http://www.daimi.au.dk/pn2000/Interchange/. June 2000.