Since a CmpFrame is itself a Frame, it can be used as a component in forming further CmpFrames. Frames of arbitrary complexity may be built from simple individual Frames in this way.
Also since a Frame is a Mapping, a CmpFrame can also be used as a Mapping. Normally, a CmpFrame is simply equivalent to a UnitMap, but if either of the component Frames within a CmpFrame is a Region (a sub-class of Frame), then the CmpFrame will use the Region as a Mapping when transforming values for axes described by the Region. Thus input axis values corresponding to positions which are outside the Region will result in bad output axis values.
"attribute and forward access requests to the component SkyFrame. Likewise, it will recognise the
"attribute and forward access requests to the component SpecFrame. An axis index can optionally be appended to the end of any attribute name, in which case the request to access the attribute will be forwarded to the primary Frame defining the specified axis.