BNF Syntax Notation

The syntax for the ESTA language is written in the formal description language called BNF. The following symbols are meta symbols with a special meaning as listed below:

::= Is interpreted as 'consists of' or 'is defined as'.

{ } Curly brackets indicate that the sequence in the

brackets may be repeated zero or more times.

[ ] Square brackets state that the sequence in the

brackets is optional.

< > Names embedded in angle brackets are syntactic

elements such as <integers>,<names>etc. All

syntactic names will be defined i.e.

they will appear on the left side of the '::='

symbol in a grammar rule.

| A vertical bar is read 'or' and is used to separate alternatives.

Example

<symbol> ::= <letter>{<letter>|<letter>|<digit>|_}

<letter> ::= a|b|c|...|x|y|z

A|B|C|...|X|Y|Z

<digit> ::= 0|1|2|3|4|5|6|7|8|9