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Petri Net based semantic engine Vivek Singh, SEECS, UCF Feb 7, 2002. What are Petri Nets? …for the uninitiated. A Petri Net is a 5 tuple (P,T,F,W,M 0 ) where P = {p 0 , p 1 , p 2 , … p m } is a finite set of places. T = {t 0 , t 1 , t 2 , … t m } is a finite set of transitions.
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Petri Net based semantic engine Vivek Singh, SEECS, UCFFeb 7, 2002
What are Petri Nets?…for the uninitiated A Petri Net is a 5 tuple (P,T,F,W,M0) where P = {p0, p1, p2, … pm} is a finite set of places. T = {t0, t1, t2, … tm} is a finite set of transitions. F is a subset of (PXT) U (TXP) .This is the set of arcs. W : F → {1,2,3…} is a weight function for the arcs. M0: P → {0,1,2,3…} is the function for initial markings. Also, the following constraints apply, P ∩T = Ø i.e. no place can be a transition and vice-versa. Pictorially, a Petri Net looks like this -
An Example of Pictorial Representation A model for the classic Reader-Writer ProblemCourtesy - Internet Based Workflow Management: Toward a Semantic Web, Dan C Marinescu, Wiley 2002, pp137.
Agent description using Petri Nets. • To be able to describe the structure of the agent in terms of a standard formal representation – Petri Nets. • Once the agent has been described formally as a (particular type of) PN, the multi plane structure can be obtained from that specification using formal techniques detailed in [4]. • Maturity of formalism • Been around for 30-35 years. • Been used for modeling in many areas. • Lots of tools available. • Industrial use of PN prevalent. Motivation…not necessarily in the order of Importance
Background • PNML at Humboldt University at Berlin. • Petri Net Markup Language [6]. Other efforts elsewhere. Standardization. • XML-based interchange format for Petri nets. • Originally for Petri Net Kernel [7]. • Source code available. • University of Hamburg at Hamburg. • Colored Petri Nets to model the structure and behavior of agents. • Similar to Bond in terms of their use of sub-protocols and multiple threads of control. • Multiplane architecture not present, however.
Objectives Phase 1 Design and Implementation of • a translator that converts a Petri Net model into an internal data structure (Use of Petri Net Kernel envisaged). • the semantic engine that takes that data structure and performs the corresponding actions (Ideas to be borrowed from [4]). Decompose the PN to multiple FSMs and represent them in form of a Blueprint. Phase 2 Integration into Bond.
Literature Survey 1. Petri Nets: Properties, Analysis and Applications. T. Murata, Proceedings of the IEEE, Vol. 77, No 4, April, 1989, pp. 541-580. - A general Introduction to Petri Nets. 2. Internet Based Workflow Management: Toward a Semantic Web, Dan C Marinescu, Wiley 2002. Chapter 3, Net Models for Distributed Systems and Workflows. - Another general Introduction to Petri Nets. 3. A Framework for Modeling Agent-Oriented Software, Haiping Xu and Sol M. Shatz, Proceedings of the 21st International Conference on Distributed Computing Systems (ICDCS-21), April 16-19, 2001, Phoenix, Arizona, USA, pp.57-64. - Among other things, illustrates the use of. Petri Nets for modeling Agent Oriented Software http://www.cs.uic.edu/~shatz/papers/icdcs01.pdf
Literature Survey 4. The Isomorphism Between a Class of Place Transition Nets and a Multi-Plane State Machine Agent Model. Krzysztof Palacz, Ladislau Boloni, and Dan C. Marinescu. Nov 1999. - Translation of agent description from Blueprint to Petri Nets and vice versa. http://citeseer.nj.nec.com/393163.html 5. Modeling the Structure and Behavior of Petri Net Agents. Michael Kohler, Daniel Moldt, Heiko Rolke. - Looks at another way to model the structure and behavior of agents which is different from bond. http://link.springer.de/link/service/series/0558/papers/2075/20750224.pdf 6. Petri Nets Markup Language www.informatik.hu-berlin.de/top/pnml/detail.html 7. Petri Net Kernel www.informatik.hu-berlin.de/top/pnk/index.html