inner path that changes direction at most once. The 2-dimensional language representing
such polyominoes has been recently proved to be recognizable by tiling systems by S.
Brocchi, A. Frosini, R. Pinzani and S. Rinaldi. In an attempt to compare recognition power of
tiling systems and cellular automata, we have proved that this language can be recognized
by 2-dimensional cellular automata working on the von Neumann neighborhood in real time …