How to read syntax diagrams

The following rules apply to the syntax diagrams used in this book:

• Read the syntax diagrams from left to right, from top to bottom, following the path of the line.

  The >>--- symbol indicates the beginning of a statement.

  The ---> symbol indicates that the statement syntax is continued on the next line.

  The >--- symbol indicates that a statement is continued from the previous line.

  The --->< symbol indicates the end of a statement.

  Diagrams of syntactical units other than complete statements start with the >--- symbol and end with the ---> symbol.

• Commands are always on the main path in the diagram. The minimum abbreviation for commands and parameters is shown in uppercase. Variables appear in lowercase italics (for example, column-name). They represent user-defined parameters or suboptions.

  When entering commands, separate the parameters and keywords by at least one space if there is no intervening punctuation.

• Enter punctuation marks (slashes, commas, periods, parentheses, quotation marks, equal signs, and so on) and numbers exactly as given.
• Footnotes are shown by a number in parentheses, for example, (1).
• Required items appear on the horizontal line (the main path).

  >>-required_item-----------------------------------------------><
  
  

• Optional items appear below the main path.

  >>-required_item--+---------------+----------------------------><
                    '-optional_item-'
  
  

• If you can choose from two or more items, they appear vertically, in a stack.

  If you are required to choose one of the items, one item of the stack appears on the main path.

  >>-required_item--+-required_choice1-+-------------------------><
                    '-required_choice2-'
  
  

  If choosing one of the items is optional, the entire stack appears below the main path.

  >>-required_item--+------------------+-------------------------><
                    +-optional_choice1-+
                    '-optional_choice2-'
  
  

  If choosing one of the items is optional but there is a default value, the default is displayed above the line.

                    .-default_choice---.
  >>-required_item--+------------------+-------------------------><
                    +-optional_choice1-+
                    '-optional_choice2-'
  
  

• If an item is repeatable, a left pointing arrow indicates a loop in the diagram. Optionally, the items can be separated with commas.

                          .-+---+---------------.
                          | '-,-'               |
                          V                     |
  >>-non-repeatable_item------repeatable_item---+----------------->
  
  >--non-repeatable_item-----------------------------------------><