(1) The settings for shell variables and paths set when the user logs in. These variables can be modified later by the user.
(2) A named collection of logical and physical resources used to support the performance of a function.
(3) A structure within the message tree that is user-defined, and that can contain variable information that is associated with a message while it is being processed by a message flow.
(4) A specific instance of a configuration of hardware and software.