Syntax  An Extended Backus-Naur Form (EBNF) specification of the syntax of a program­ ming language consists of a collection of rules or productions collectively called a  "grammar" that describe the formation of sentences in the language. Each production  consists of a non-terminal symbol and an EBNF expression separated by an equal sign  and terminated with a period. The non-terminal symbol is a "meta-identifier" (a syn­ tactic constant denoted by an English word), and the EBNF expression is its definition.  The EBNF expression is composed of zero or more terminal symbols, non-terminal  symbols, and other metasymbols summarized in this table:  MetaSymbol  Meaning  [X]  {X}  (XI  Y)  "XYZ"  Meta-Identifier  is defined to be  alternatively  end of production  o or 1 instance of X  o  or more instances of X  a grouping: either X or  Y  the terminal symbol XY Z  the non-terminal symbol  Metaldentifier  Syntax  Production  Expression  Term  Factor  Terminal  NonTerminal  = {  Production  } .  =  NonTerminal  "="  Expression  H." .  =  Term  [  HI"  Term] .  = Factor  {  Factor} .  =  NonTerminal1 Terminal  I H("  Expression  H)"  H["  Expression  HJ"  H {"  Expression  H}" .  =  HHH"  Character  {  Character}  '''''''' .  = Letter  {  Letter  I  Digit} .  As an example, EBNF can be used to define its own syntax.  213  APPENDIXD 