Syntax diagrams

The following rules apply to syntax diagrams:

	>>-required-item---------------------><
	>>-required-item--+----------------+-----><
                          '-optional-item--'
	>>-required-item--+-required-choice1-+--+------------------+--><
                          '-required-choice2-'  +-optional-choice1-+
                                                '-optional-choice2-'
                          .-default-optional-choice-.
	>>-required-item--+-------------------------+--><
                          +-optional-choice1--------+
                          '-optional-choice2--------'