formulate the robot map navigation problem (AKA the maze, or the grid)

We would like to formulate the robot map navigation problem (AKA the maze, or the grid). You have a map consisting of a grid of square cells. some of the cells are blocked (obstacles that the robot cannot walk through) and some are empty (free areas). The robot is located at one of the empty cells, and it wants to go to a goal cell. The robot is allowed to move one step at a time. The possible moves are to the north, south, east, and west.