Notation

• Syntactic categories (or nonterminals) are printed in italics, for example query. Depending on the section, a category may represent a class of either terms, token lists, or character strings.
• A syntactic rule takes the general form

            C --> F1
                 | F2
                 | F3
                 .
                 .
                 .
            

  which states that an entity of category C may take any of the alternative forms F1, F2, or F3.

• Certain definitions and restrictions are given in ordinary English, enclosed in braces ({}).
• A category written as C... denotes a sequence of one or more Cs.
• A category written as ?C denotes an optional C. Therefore ?C... denotes a sequence of zero or more Cs.
• A few syntactic categories have names with arguments, and rules in which they appear may contain meta-variables in the form of italicized capital letters. The meaning of such rules should be clear from analogy with the definite clause grammars described in ref-gru.
• In ref-syn-syn-trm, particular tokens of the category Name (a name beginning with a capital letter) are written as quoted atoms, while tokens that are individual punctuation characters are written literally.