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. 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, pp137.

Motivation …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 in terms of a standard formal representation – 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]. 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 Maturity of formalism Been around for years. Been around for 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 PNML at Humboldt University at Berlin. PNML at Humboldt University at Berlin. Petri Net Markup Language [6]. Other efforts elsewhere. Standardization. Petri Net Markup Language [6]. Other efforts 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 behavior of agents. 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. Similar to Bond in terms of their use of sub-protocols and multiple threads of control. Multiplane architecture not present, however. 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). 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. 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 A general Introduction to Petri Nets. 2. Internet Based Workflow Management: Toward a Semantic Web, Dan C Marinescu, Wiley 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 Among other things, illustrates the use of. Petri Nets for modeling Agent Oriented Software

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 Translation of agent description from Blueprint to Petri Nets and vice versa 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 Petri Nets Markup Language 7. Petri Net Kernel Literature Survey