Subprocess descriptors

A facility provided by the directory system for use by the higher levels of the system was that of subprocess descriptors. There was a need to construct a subprocess within a users process, at the request of a user, which had access to capabilities not available to the user. One purpose of this was to provide for actions which manipulated objects within the system to which the user could not be given direct access. A subprocess descriptor was simply a capability for a directory, but with a different type. An action was provided to the higher levels of the system, not made available to the users, which could convert this capability into a directory capability. One of the actions to be provided by a higher level of the system was to take such a capability, convert it to a directory capability, look up a special name within the directory, take the resulting capability to be that of a disk file; and interpret the contents of that disk file as a description of a subprocess to be built within the users process. Part of this description would be text names. During construction of the subprocess (done by the command processor, see chapter 13) these names would be looked up in the directory defined by the subprocess descriptor, and the resulting capabilities were placed in the local C-list of the new subprocess.