Petri Net based semantic engine Vivek Singh SEECS
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, … pm} is a finite set of places. T = {t 0, t 1, t 2, … 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. M 0: 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 Problem Courtesy - Internet Based Workflow Management: Toward a Semantic Web, Dan C Marinescu, Wiley 2002, pp 137.
Motivation …not necessarily in the order of Importance 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.
Background l PNML at Humboldt University at Berlin. l Petri Net Markup Language [6]. Other efforts elsewhere. Standardization. l XML-based interchange format for Petri nets. l Originally for Petri Net Kernel [7]. l Source code available. l University of Hamburg at Hamburg. l Colored Petri Nets to model the structure and behavior of agents. l Similar to Bond in terms of their use of sub-protocols and multiple threads of control. l 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). l 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. l 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 21 st 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/icdcs 01. 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/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
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