Call-out Bracket Methods in Timor

This paper extends the concept of qualifying types by describing how their implementations can include not only bracket methods which are applied when a method of a target object is invoked, but also further "call-out " bracket methods which can be applied to invocations by the target object of the methods of other objects. This additional technique can be used for example to provide enhanced synchronisation in qualifying types, as an aid to confining the activities of an object, and as a means of providing parallel activities associated with the sending and receiving of information, e.g. encryption and decryption, data compression.