A service providing method, wherein a first information processing apparatus provides a first service and a second information processing apparatus provides a second service, the method comprising: at a third information processing apparatus, authenticating a user according to an authenticating request received from a terminal apparatus in use by the user; at the third information processing apparatus, upon successful authentication of the user, determining a role, in a third service, assigned to the user who is using the terminal apparatus from which the authentication request has been sent, with reference to a role definition that indicates a role in the third service for each user; at the third information processing apparatus, sending, to the terminal apparatus, third role information that indicates the third service provided by the third information processing apparatus and the determined third role assigned to the user in the third service; at the second information processing apparatus, receiving the third role information from the terminal apparatus in use by the user; at the second information processing apparatus, determining a role assigned to the user in the second service according to the third role information received by the second information processing apparatus and trust-relationship information that indicates a direct trust-relationship between the second information processing apparatus and the third information processing apparatus, in correspondence to the third service; at the second information processing apparatus, sending second role information indicating the second service provided by the second information processing apparatus and the role assigned to the user in the second service to the terminal apparatus; at the first information processing apparatus, receiving, from the terminal apparatus in use by the user, the second role information; at the first information processing apparatus, determining a role assigned to the user in the first service according to the received second role information and trust-relationship information that indicates a direct trust-relationship between the first information processing apparatus and the second information processing apparatus, in correspondence to the second service; and at the first information processing apparatus, executing processing of the first service within a range of a service allowed according to the role determined at the first information processing apparatus, with reference to a said service definition in which a range of a service allowed according to a role and provided by the first information processing apparatus is defined, wherein a role, assigned to a user for the use of a service, defines the level of access to information provided to the user for said service. at a third information processing apparatus, authenticating a user according to an authenticating request received from a terminal apparatus in use by the user; at the third information processing apparatus, upon successful authentication of the user, determining a role, in a third service, assigned to the user who is using the terminal apparatus from which the authentication request has been sent, with reference to a role definition that indicates a role in the third service for each user; at the third information processing apparatus, sending, to the terminal apparatus, third role information that indicates the third service provided by the third information processing apparatus and the determined third role assigned to the user in the third service; at the second information processing apparatus, receiving the third role information from the terminal apparatus in use by the user; at the second information processing apparatus, determining a role assigned to the user in the second service according to the third role information received by the second information processing apparatus and trust-relationship information that indicates a direct trust-relationship between the second information processing apparatus and the third information processing apparatus, in correspondence to the third service; at the second information processing apparatus, sending second role information indicating the second service provided by the second information processing apparatus and the role assigned to the user in the second service to the terminal apparatus; at the first information processing apparatus, receiving, from the terminal apparatus in use by the user, the second role information; at the first information processing apparatus, determining a role assigned to the user in the first service according to the received second role information and trust-relationship information that indicates a direct trust-relationship between the first information processing apparatus and the second information processing apparatus, in correspondence to the second service; and at the first information processing apparatus, executing processing of the first service within a range of a service allowed according to the role determined at the first information processing apparatus, with reference to a said service definition in which a range of a service allowed according to a role and provided by the first information processing apparatus is defined, wherein a role, assigned to a user for the use of a service, defines the level of access to information provided to the user for said service.