The present invention relates to a computer system having a user interface through which a user can select an action in order to invoke a desired operation, and to a method of operation of such a computer system. The action is selectable by one or more views provided via the user interface, and the system comprises generation means for representing an action by an action object, the action object defining, for each available view that can be employed to represent that action, the attributes required to provide that view, and an identifier to identify the operation to be invoked upon selection of the action. Further the system comprises identifying means for identifying when a user selection of a view has occurred, and for informing the associated action object of that selection, and the action object is responsive to the identifying means to employ the unique identifier to generate a command to invoke the desired operation. In preferred embodiments, the computer system is connectable to a display device to display a graphical user interface, and at least one of the views that can be employed to represent the action is a visual view displayable via the graphical user interface, the attributes defined in the action object for said at least one of the views including data required to produce the visual view. The computer system achieves single event generation from multiple views, and therefore the application does not need to concern itself with how the user generated the call. The action views query the attributes of the action object directly, all the necessary data is held in one place, and with automatic view concurrency, the application developer no longer has to worry about keeping action views synchronised with each other.