UML14 — Appendix A of the superstructure spec

Appendix A of the superstructure spec specify the usage of frames
in diagrams. The text says:
"Each diagram has a frame, a contents area, and a heading, see Figure 460."

This statement implies that frames are normative. The text later says
that "In cases where not needed, the frame may be omitted and implied by the border of the diagram area provided by a tool."

This entire explanation distorts the common intent and practice of UML
diagramming. Text should present the frames as an optional presentation
option in the first place. Also, in all cases mentioned (ports, entry points)
it is possible to notate the context using class boxes or states, so in none of these cases frames are "needed". It is a mere presentation option that might be

used as an alternative to using prime container symbols.

see above