108 Chapter 6. Notation · Production Syntax · Regular Expression Operators This chapter explains the rules of the formal grammar used in the specification\xd5 s productions. The formal grammar of XML is given in this specification using a simple Extended Backus-Naur Form (EBNF) notation. Each rule in the grammar defines one symbol, in the form symbol ::= expression This section of the spec describes the syntax used by the productions to show the possible makeup of each component of an XML document. "" in the "Supplementary Annotations" appendix of this