[EN] The calculation of the smallest number of steps needed to deterministically reach all local states of an nth-order positive 2-D system, which is called local reachability index (ILR) of that system, was recently tackled ...
Bailo Ballarín, Esteban Antonio; Gelonch Anye, Jose; Romero Vivó, Sergio(Institute of Electrical and Electronics Engineers (IEEE), 2014)
The problem of obtaining an upper bound on the local reachability index I_LR for a positive 2-D system is still an unanswered question. Unfortunately, it is not clear what kind of mathematical instruments should be used ...