[[Grammar Overrides]] refer to nonterminal modifications or extensions to a fixed base grammar for the purpose of extending the language or customizing the parse to the task ([[Agile Parsing]]).  [[Grammar Overrides]] are most obvious and convenient in [[http://www.program-transformation.org/Transform/TXL][TXL]], which has an explicit feature for implementing them, but are a general concept used in many source transformation systems.  They can be implemented any number of ways including using [[Grammar Adaptation]], [[Grammar Transformation]] or by hand using cloning of the original base grammmar.

-- Main.JamesCordy - 10 Oct 2005