NANJING UNIVERSITY Petri Nets Lei Bu .1
Lei Bu Petri Nets 1
效鼎 Dining Philosphier 4 States,5 transitions put_1 IF1 1F1 1_get_F2 F1 1_get_F1 11F2 IF1 F2 1F2 11F1 1F1 11F2 1F2 M出果 1_get_F2 F1 1_get_F1 IF2 11_F1 1F2
Dining Philosphier ◼ 4 States， 5 transitions
效绵 9 States 14 Transitions 1利 2 put_back 1 put back 2.get_F1 02 1-geLF1 2.90tF2 19做F2 1F1 11 NF2 F2 2程 2_get_F2 198LF2 19tF2 1_get_F1 2.get_F2 1_got_F1 2_get_F1 2 get F1 F 1F1 宝 2 22
◼ 9 States 14 Transitions
效绵 27 States,56 Transitions F2 F1 F1 F2 F3 F3 F2 1F1 1F2 F 2F3 3F3 F3 F3 F2 F2 F3 F3 F2 1F1 1F 1F2 1F2 1F2 2F 2F2 2F3 2F3 3F1 1F2 2F2 2F3 3F3 2F3 3F3 3F1 3F3 2F3 3F3 1 F1 2F2 1F2 2F2 1F2 2F3 F F3
◼ 27 States， 56 Transitions
效鼎 81 States,252 Transitions 的前o白色 自dr电通©o百尚电通
◼ 81 States， 252 Transitions
效绵鼎 From automata to Petri Net automata are a theoretical and idealised model they reflect a Newtonian world-view: space time as an absolute frame of reference clockwork view of processes within this frame Carl Adam Petri has made an attempt to combine automata from theoretical CS,and pragmatic expertise from engineers:Petri Net state is distributed,transitions are localised local causality replaces global time subsystems interact by explicit communication
• automata are a theoretical and idealised model • they reflect a Newtonian world-view: • space & time as an absolute frame of reference • clockwork view of processes within this frame • Carl Adam Petri has made an attempt to combine automata from theoretical CS, and pragmatic expertise from engineers: Petri Net From automata to Petri Net • state is distributed, transitions are localised • local causality replaces global time • subsystems interact by explicit communication
效绵鼎 Petri nets-Motivation In contrast to state machines,state transitions in Petri nets are asynchronous.The ordering of transitions is partly uncoordinated;it is specified by a partial order. Therefore,Petri nets can be used to model concurrent distributed systems. Many flavors of Petri nets are in use,e.g. 0 Activity charts(UML) o Data flow graphs and marked graphs 7
Petri nets-Motivation ◼ In contrast to state machines, state transitions in Petri nets are asynchronous. The ordering of transitions is partly uncoordinated; it is specified by a partial order. ◼ Therefore, Petri nets can be used to model concurrent distributed systems. ◼ Many flavors of Petri nets are in use, e.g. Activity charts(UML) Data flow graphs and marked graphs 7
效绵 History 1962:C.A.Petri's dissertation(U.Darmstadt,W.Germany) ■ 1970:Project MAC Conf.on Concurrent Systems and Parallel Computation(MIT,USA) 1975:Conf.on Petri Nets and related Methods(MIT,USA) 1979:Course on General Net Theory of Processes and Systems (Hamburg,W.Germany） 1980:First European Workshop on Applications and Theory of Petri Nets (Strasbourg,France) 1985:First International Workshop on Timed Petri Nets(Torino,Italy)
History ◼ 1962: C.A. Petri’s dissertation (U. Darmstadt, W. Germany) ◼ 1970: Project MAC Conf. on Concurrent Systems and Parallel Computation (MIT, USA) ◼ 1975: Conf. on Petri Nets and related Methods (MIT, USA) ◼ 1979: Course on General Net Theory of Processes and Systems (Hamburg, W. Germany) ◼ 1980: First European Workshop on Applications and Theory of Petri Nets (Strasbourg, France) ◼ 1985: First International Workshop on Timed Petri Nets (Torino, Italy)
效绵县 Introduction Petri Nets:Graphical and Mathematical modeling tools 0 graphical tool ■ visual communication aid o mathematical tool state equations,algebraic equations,etc concurrent,asynchronous,distributed,parallel, nondeterministic and/or stochastic systems
Introduction ◼ Petri Nets: Graphical and Mathematical modeling tools graphical tool ◼ visual communication aid mathematical tool ◼ state equations, algebraic equations, etc ◼ concurrent, asynchronous, distributed, parallel, nondeterministic and/or stochastic systems
效绵 Informal Definition ■ The graphical presentation of a Petri net is a bipartite graph There are two kinds of nodes o Places:usually model resources or partial state of the system o Transitions:model state transition and synchronization Arcs are directed and always connect nodes of different types Tokens are resources in the places
Informal Definition ◼ The graphical presentation of a Petri net is a bipartite graph ◼ There are two kinds of nodes Places: usually model resources or partial state of the system Transitions: model state transition and synchronization ◼ Arcs are directed and always connect nodes of different types ◼ Tokens are resources in the places