Petri Net based semantic Petri Net based semantic engine engine

Vivek Singh, SEECS, UCFVivek Singh, SEECS, UCFFeb 7, 2002Feb 7, 2002

What are Petri Nets?What are Petri Nets?…for the uninitiated…for the uninitiated

A Petri Net is a 5 tuple (P,T,F,W,MA Petri Net is a 5 tuple (P,T,F,W,M00))wherewhere

P = {pP = {p00, p, p11, p, p22, … p, … pmm} is a finite set of places.} is a finite set of places.

T = {tT = {t00, t, t11, t, t22, … t, … tmm} is a finite set of transitions.} is a finite set of transitions.F is a subset of (PXT) U (TXP) .This is the set of arcs.F is a subset of (PXT) U (TXP) .This is the set of arcs.W : F W : F → {1,2,3…} is a weight function for the arcs.→ {1,2,3…} is a weight function for the arcs.

MM00: P → {0,1,2,3…} is the function for initial markings.: P → {0,1,2,3…} is the function for initial markings.

Also, the following constraints apply,Also, the following constraints apply,P ∩T = Ø i.e. no place can be a transition and vice-P ∩T = Ø i.e. no place can be a transition and vice-

versa.versa.

Pictorially, a Petri Net looks like this -Pictorially, a Petri Net looks like this -

An Example of Pictorial An Example of Pictorial RepresentationRepresentation

A model for the classic Reader-Writer ProblemA model for the classic Reader-Writer Problem

Courtesy - Internet Based Workflow Management: Toward a Semantic Web, Dan C Marinescu, Courtesy - Internet Based Workflow Management: Toward a Semantic Web, Dan C Marinescu, Wiley 2002, pp137.Wiley 2002, pp137.

MotivationMotivation…not necessarily in the order of Importance…not necessarily in the order of Importance

Agent description using Petri Nets. Agent description using Petri Nets. To be able to describe the structure of the agent To be able to describe the structure of the agent

in terms of a standard formal representation – in terms of a standard formal representation – Petri Nets.Petri Nets.

Once the agent has been described formally as Once the agent has been described formally as a (particular type of) PN, the multi plane a (particular type of) PN, the multi plane structure can be obtained from that specification structure can be obtained from that specification using formal techniques detailed in [4].using formal techniques detailed in [4].

Maturity of formalismMaturity of formalism Been around for 30-35 years.Been around for 30-35 years. Been used for modeling in many areas.Been used for modeling in many areas. Lots of tools available.Lots of tools available. Industrial use of PN prevalent. Industrial use of PN prevalent.

Background Background PNML at Humboldt University at Berlin.PNML at Humboldt University at Berlin.

Petri Net Markup Language [6]. Other efforts Petri Net Markup Language [6]. Other efforts elsewhere. Standardization.elsewhere. Standardization.

XML-based interchange format for Petri nets.XML-based interchange format for Petri nets. Originally for Petri Net Kernel [7].Originally for Petri Net Kernel [7]. Source code available. Source code available.

University of Hamburg at Hamburg.University of Hamburg at Hamburg. Colored Petri Nets to model the structure and Colored Petri Nets to model the structure and

behavior of agents. behavior of agents. Similar to Bond in terms of their use of sub-Similar to Bond in terms of their use of sub-

protocols and multiple threads of control. protocols and multiple threads of control. Multiplane architecture not present, however.Multiplane architecture not present, however.

ObjectivesObjectives

Phase 1Phase 1

Design and Implementation of Design and Implementation of a translator that converts a Petri Net model into an a translator that converts a Petri Net model into an

internal data structure internal data structure (Use of Petri Net Kernel (Use of Petri Net Kernel envisaged)envisaged) . .

the semantic engine that takes that data structure and the semantic engine that takes that data structure and performs the corresponding actions (Ideas to be performs the corresponding actions (Ideas to be borrowed from [4]). Decompose the PN to multiple borrowed from [4]). Decompose the PN to multiple FSMs and represent them in form of a Blueprint.FSMs and represent them in form of a Blueprint.

Phase 2Phase 2Integration into Bond.Integration into Bond.

Literature SurveyLiterature Survey1. Petri Nets: Properties, Analysis and Applications. T. 1. Petri Nets: Properties, Analysis and Applications. T.

Murata, Proceedings of the IEEE, Vol. 77, No 4, April, Murata, Proceedings of the IEEE, Vol. 77, No 4, April, 1989, pp. 541-580.1989, pp. 541-580.- A - A general Introductiongeneral Introduction to Petri Nets. to Petri Nets.

2. Internet Based Workflow Management: Toward a 2. Internet Based Workflow Management: Toward a Semantic Web, Dan C Marinescu, Wiley 2002. Chapter Semantic Web, Dan C Marinescu, Wiley 2002. Chapter 3, Net Models for Distributed Systems and Workflows.3, Net Models for Distributed Systems and Workflows.- Another - Another general Introductiongeneral Introduction to Petri Nets. to Petri Nets.

3. A Framework for Modeling Agent-Oriented Software, 3. A Framework for Modeling Agent-Oriented Software, Haiping Xu and Sol M. Shatz, Haiping Xu and Sol M. Shatz, Proceedings of the 21st Proceedings of the 21st International Conference on Distributed Computing International Conference on Distributed Computing Systems (ICDCS-21)Systems (ICDCS-21), April 16-19, 2001, Phoenix, , April 16-19, 2001, Phoenix, Arizona, USA, pp.57-64. Arizona, USA, pp.57-64. - Among other things, illustrates the use of. - Among other things, illustrates the use of. Petri Nets Petri Nets for modeling Agent Oriented Softwarefor modeling Agent Oriented Softwarehttp://www.cs.uic.edu/~shatz/papers/icdcs01.pdfhttp://www.cs.uic.edu/~shatz/papers/icdcs01.pdf

4. The Isomorphism Between a Class of Place Transition Nets 4. The Isomorphism Between a Class of Place Transition Nets and a Multi-Plane State Machine Agent Model.  Krzysztof and a Multi-Plane State Machine Agent Model.  Krzysztof Palacz, Ladislau Boloni, and Dan C. Marinescu. Nov 1999.Palacz, Ladislau Boloni, and Dan C. Marinescu. Nov 1999.- - TranslationTranslation of agent description of agent description from Blueprint to Petri from Blueprint to Petri Nets and vice versa.Nets and vice versa.http://citeseer.nj.nec.com/393163.htmlhttp://citeseer.nj.nec.com/393163.html

5. Modeling the Structure and Behavior of Petri Net Agents. 5. Modeling the Structure and Behavior of Petri Net Agents. Michael Kohler, Daniel Moldt, Heiko Rolke. Michael Kohler, Daniel Moldt, Heiko Rolke. - Looks at another way to - Looks at another way to model the structure and behavior of model the structure and behavior of agentsagents which is different from bond. which is different from bond.http://link.springer.de/link/service/series/0558/papers/http://link.springer.de/link/service/series/0558/papers/2075/20750224.pdf2075/20750224.pdf

6. Petri Nets Markup Language 6. Petri Nets Markup Language www.www.informatikinformatik.hu-berlin.de/top/pnml/detail.html.hu-berlin.de/top/pnml/detail.html

7. Petri Net Kernel 7. Petri Net Kernel www.www.informatikinformatik.hu-berlin.de/top/pnk/index.html.hu-berlin.de/top/pnk/index.html

Literature SurveyLiterature Survey