XT

Transformation systems consist of many aspects including parsing, tree manipulation, and pretty-printing. Reimplementation of components for all aspects is expensive; reuse of existing components is desirable.

This requires a format for the exchange of data between components and availability of the source code of the components such that modifications can be made if necessary.

• The Online Package Base: an interactive collection of packages that bundles packages on demand
• XT: A bundle of tools for program transformation