It is proposed to compare strategies in a parity game by comparing the sets of behaviours they allow. For such a game, there may be no winning strategy that encompasses all the behaviours of all winning strategies. It is shown, however, that there always exists a permissive strategy that encompasses all the behaviours of all memoryless strategies. An algorithm for finding such a permissive strategy is presented. Its complexity matches currently known upper bounds for the simpler problem of finding the set of winning positions in a parity game. The algorithm can be seen as a reduction of a parity to a safety game and computation of the set of winning positions in the resulting game.
@article{ITA_2002__36_3_261_0, author = {Bernet, Julien and Janin, David and Walukiewicz, Igor}, title = {Permissive strategies : from parity games to safety games}, journal = {RAIRO - Theoretical Informatics and Applications - Informatique Th\'eorique et Applications}, volume = {36}, year = {2002}, pages = {261-275}, doi = {10.1051/ita:2002013}, mrnumber = {1958243}, zbl = {1090.91514}, language = {en}, url = {http://dml.mathdoc.fr/item/ITA_2002__36_3_261_0} }
Bernet, Julien; Janin, David; Walukiewicz, Igor. Permissive strategies : from parity games to safety games. RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications, Tome 36 (2002) pp. 261-275. doi : 10.1051/ita:2002013. http://gdmltest.u-ga.fr/item/ITA_2002__36_3_261_0/
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