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.
<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