Currently there are a number of functions corresponding to path-handling
in the LOCATABLE class, including the parent property. However, some classes
in the RM, such as EVENT_CONTEXT, ISM_TRANSITION and INSTRUCTION_DETAILS do
not inherit from LOCATABLE, but still need to be able to handle paths, since
they contain ITEM_STRUCTURE attributes. In general, there is a need to
make classes all the way down to the ultimate leaves, which are data types
and primitive types, path-enabled.