Abstract: Provided is a scheme for implementing flexible control of subject authorizations (i.e. the authorizations which users or processes have) to perform operations in relation to computer resources. The methods, computer systems and authorization facilities which are provided by the invention enhance the security provisions of operating systems which have only very limited authorization facilities, by mapping the available operating system permissions to specified resource authorities for each of a set of aspects or characteristics of a computer system resource. Thus, the standard operating system permissions (e.g. read, write, execute) can have different meanings for different resource aspects, and an individual subject can have separate authorization levels set for the different resource aspects. The mappings between authorities and the available permissions may be different for different types of resources.

Abstract: The Data communication systems and methods in which information for routing of messages between nodes of a communications network is provided by a directory service (such as the DCE directory service), accessible from all network nodes. The provision of such information by the directory service removes the requirement for routing tables to be set up and maintained at each of the network nodes, whose maintenance can involve considerable network traffic in dynamically changing networks or problems of inconsistent data being held at different nodes.