We now turn to a rather special form of MappingMapping, the CmpFrameCmpFrame. The Frames we have considered so far have been atomic, in the sense that they represent pre-defined elementary physical domains. A CmpFrame, however, is a compound FrameFrame. In essence, it is a structure for containing other Frames and its purpose is to allow those Frames to work together in various combinations while appearing as a single ObjectObject. A CmpFrame's behaviour is therefore not pre-defined, but is determined by the other Frames it contains (its “component” Frames).
As with compound Mappings, compound Frames can be nested within each other, forming arbitrarily complex Frames.