Home > Storage > PowerScale (Isilon) > Product Documentation > Management and Migration > PowerScale OneFS User Mapping: Mapping Identities Across Authentication Providers > Direction of a rule
A rule applies in one of three directions: left to right, bidirectional, or unary. The rule’s direction determines how the user mapping service matches the usernames in the rule and modifies the token.
Direction | Description |
Left to Right | A left to right rule contains two usernames. The mapper compares the first username with the token. If the first username matches the token, the mapping service expands the wildcards of the second username and then resolves the second username by looking it up in the authentication providers. If the lookup finds the second username, the mapping service applies the rule. |
Bidirectional | A bidirectional rule contains two usernames. If the first username matches the token, the mapping service evaluates the rule as a left to right rule. If the second username matches the token, the service expands the wildcards in the first user and resolves the first user before applying the rule. |
Unary | A unary rule contains only one username. If the username matches an identity, the mapping service applies the rule. |