In providing services in an environment in which apparatuses constituting
a system change dynamically, flexible control of access control is
performed for the apparatuses whose access rights and service providing
policies are different or have not been set beforehand. In a distributed
system where computers each having a function of storing data and
processing a program and a communication facility perform data exchange
through a communication medium, and thereby perform processing, control
of limiting an access to the system etc. is performed as a shared session
that is established by synthesizing access rights and service providing
policies owned by the apparatuses, and accesses to the apparatuses and
provision of services are performed through the shared session, whereby
the access rights and the services to be provided are controlled
according to a configuration of apparatuses constituting the system.