Abstract: A computer implemented method of defining an object union in an object oriented programming environment, comprising the steps of: selecting a first class from which a first object to be contained in the object union will be instantiated at runtime; selecting a second class from which a second object to be contained in the object union will be instantiated at runtime; selecting a policy function for operating on the first and second classes, at runtime, in order to define which methods supported by the first and second classes will be accessible via the object union at runtime.

Abstract: A desktop manager for a multi-processing graphic user interface operating system operates to control the display of a plurality of controls each occupying respective display areas on a desktop. An improved desktop manager characterised by means adapted to receive a request for urgency from a process owning a control; and means adapted to diminish the display of one or more of any other controls to draw the attention of a user to the control owned by the process requesting urgency is disclosed.

Abstract: A file system for a computer supports a plurality of directories, each maintaining a list of data files as a plurality of directory entries. As well as means for creating data entries for real data files, the system includes means for creating anti-file directory entries having an attribute indicating there is no real data file corresponding to the entry. Entries may-be moved between directories and when an anti-file and a data file of the same name are present in the same directory, the real data file is deleted. This enables the synchronization of sets of target and source files to take account of changes.