The rules are written in the twin programming languages called CHMTRN and PATRAN originally developed in the LHASA project . CHMTRN is probably best described as a hybrid of FORTRAN style programming with numerous buzz words providing a natural-language-like representation of detailed synthetic chemistry knowledge. It is used together with PATRAN, a chemical pattern description language. CHMTRN/PATRAN surpass other reaction transform descriptions such as SMIRKS in several respects: (1) Structural features that may be important for the reaction but are remote from the reaction center can be described and tested for (such as "a hydroxyl group within two atoms of one of the reaction center atoms"); (2) control and conditional functionality (such as "if ... then .. else", and "for each") and subroutine usage are possible; (3) tests for structural elements other than atoms and bonds, e.g. physico-chemical properties (such as electrophilic localization energy) can be implemented; (4) scoring systems can be implemented.