Players can organize themselves into corporations (similar to guilds or clans in other MMOs). Their status in healers' guilds were often challenged. The pochteca were specialized long distance merchants organized into exclusive guilds. The status of women in the old guilds and corporations of medieval masons remains uncertain. Trade was carried on by merchants organised in guilds. Skilled workers were often politically active through their craft guilds. Those tournaments are held between guilds, groups of players that fight together against other guilds. The companies originated as guilds or trade associations. These initially were merchant guilds, but developed into separate trade guilds for each skill. Other guilds, such as the SAG-AFTRA act as trade unions rather than as classical guilds. The best were adopted and recognised as members of various art guilds. Traditional arbitration involved heads of trade guilds or other dominant authorities settling disputes. Credits were obtained from religious orders and merchant guilds. Other early guilds included the "craft guilds", representing specific trades. Membership in these early guilds was voluntary.