Grammars and BNF Notation

A step past regexps and markup languages are full grammars in Backus Naur Form (BNF), most commonly used for parsing programming languages. They're also useful in protocol documents (e.g., the documentation for the HTTP standard that describes communication between web browsers and web servers; see http://www.w3.org/protocols/rfc1945/rfc1945) as a flexible means of enumerating the structure of a protocol. An example of a grammar for U.S. postal addresses (http://en.wikipedia.org/wiki/backus%e2%80%93naur_form) follows:

<postal-address> ::= <name-part> <street-address> <zip-part>

     <name-part> ::= <personal-part> <last-name> <opt-jr-part> <EOL>
                   | <personal-part> <name-part> <EOL>

 <personal-part> ::= <first-name> | <initial> "."

<street-address> ::= <opt-apt-num> <house-num> <street-name> <EOL>

      <zip-part> ::= <town-name> "," <state-code> <ZIP-code> <EOL>