35. The apparatus of claim 11 and wherein and wherein the objects comprise host objects and guest objects, and the user interface allows a user to perform a backspace operation which reverses the infix entry sequence for guest objects of the non-primitive object in one of whose fields the cursor is located, sequentially removing primitive objects which precede the cursor, and once the cursor reaches a first slot with respect to the slot sequence of the slots contained in the fields of the host object in which the cursor is currently located, backspacing is disabled if the non-primitive object still contains any guest objects.
11. The apparatus of claim 2 and wherein: the objects comprise host objects and guest objects; the single computer readable data structure is capable of representation by an object-field diagram comprising a primary sequence of said objects, subsequences of which are organized into the fields, and for each non-primitive object its fields are ordered with respect to an infix entry sequence; the object field diagram further identifies the slots; indices are assigned to the objects which give the order of the objects as entered by the user using the infix entry sequence; and the infix entry process defines a slot sequence of the slots.