Parser building is a powerful programming technique that opens a world of opportunity for designing how users interact with applications. By creating mini-languages, you can precisely address the requirements of your application development domain. Writing your own parsers empowers you to access a database more effectively than SQL to efficiently control the movement of an order through its workflow, to command the actions of a robot, and to control access privileges to transactions in a system. The repertoire of today’s professional programmer should include the know-how to create custom languages.