//This model is inspired by the vacuum cleaning world example described by Michael Wooldridge
//in his book "An Introduction to Multi Agent Systems, p52-54.
//Model made by Frits Vaandrager, Radboud University Nijmegen, February 2014
//The idea is simple: we let the robot just take "turn" and "forward" moves nondeterministically.
//We store the choice made for each location/orientation pair. The robot may only make this move once
//during its first cycle through the room.
//Uppaal does not support enumerated types so we encode some constants as integers
//CONSTANTS
//size of toom
const int n=3;
//strtaegy values
const int undefined = 0;
const int turn = 1;
const int forward = 2;
//directions
const int N = 3;
const int E = 4;
const int S = 5;
const int W = 6;
//TYPES
// range of x, y positions
typedef int[0,n-1] pos;
// range of directions: the set {N, E, S, W}
typedef int[N,W] dir;
// range of strateggy values: the set {free, turn, forward}
typedef int[undefined,forward] strategy_values;
dir rotate(dir direction){
return (direction==N)?E:((direction==E)?S:((direction==S)?W:N));
}
//CHANNELS
// just to give transitions a name
broadcast chan turn_act;
broadcast chan forward_act;
//STATE VARIABLES
//x coordinate of robot
pos x;
//y coordinate of robot
pos y;
//orientation of robot
dir d;
//the state variable "strategy" gives the strategy as it has been defined thus far,
//that is, given a position and an orientation for which the strategy is defined, it tells whether the robot should turn or move forward.
strategy_values strategy[pos][pos][dir];
//AUXILIARY STUFF ONLY NEEDED TO STATE PROPERTIES
//function used for stating properties
//when the robot has visited a square in the room then for at least one of the four orientations the strategy for that square must be defined
bool visited(pos x1, pos y1){
return strategy[x1][y1][N] != undefined || strategy[x1][y1][E] != undefined || strategy[x1][y1][S] != undefined || strategy[x1][y1][W] != undefined;
}
//These are auxiliary variable used to count the number of turns and forward moves in a run
int tcount, fcount;
RobotDummy//The sole purpose of the Dummy automaton is that in the counterexample traces generated by Uppaal
//the action (Turn or Forward) is visible. It should be easy to write a script that plots the
//diagrams from the Uppaal traces.
system Robot, Dummy;
progress
{
fcount+tcount;
}