Implementations
The first CG implementation was CGP by Fred Karlsson. It was purely LISP-based, and the syntax was based on LISP s-expressions (Karlsson 1990). Pasi Tapanainen's CG-2 implementation mdis removed some of the parentheses in the grammar format and was implemented in C++, interpreting the grammar as a finite state transducer for speed.
CG-2 was later reimplemented by the VISL group at Syddansk Universitet as the open source VISL CG . This project later turned into VISL CG-3, which brought further changes and additions to the grammar format, e.g. named relations and variable-setting. Unlike the Tapanainen implementation, the VISL implementations do not use finite state transducers (rules are ordered within sections, at the cost of slower parsing).
Read more about this topic: Constraint Grammar