1962

Petri net

• At the age of thirteen,
• Carl Adam Petri
• invented a graphic tool
• for modeling chemical processes.
• Circular symbols
• represent states,
• rectangular symbols
• represent transitions,
• directed arcs
• connect them,
• and tokens
• represent objects
• that exist in states.
• Transitions may “fire”
• concurrently
• when their input states
• have sufficient tokens.
• When a transition fires,
• it consumes tokens in input states
• and creates tokens
• in output states.

Automata

• A bounded Petri net
• can be modeled as a finite-state machine
• in which nodes of the machine
• represent the reachable states of the net.
• Both are kinds of automata, that is,
• models or simulations of a process.
• Conditions, materials, and actions
• have their own behaviors like living things.

The same

• For many things the thing itself and its simulation are the same.