Extensible attribute grammars

Abstract

This report introduces a new idea to make attribute grammars (AG) extensible. Both the context-free grammar and the attribution system of an AG may be extended. This concept is a valuable structuring technique when defining language-based programming environments or compilers. For instance, it allows passes of a multipass compiler to be decomposed into different grammar levels, which renders the definition much clearer. Another application consists of defining an interface for an external tool (browser) on an independent grammar level neatly separated from the actual language definition. The concept of extensible attribute grammars is first introduced using a formal model, and thereafter practical examples demonstrate possible applications.