Source code describing a part of a small example in BNGL. In BNGL, model elements are specified in blocks enclosed in tags. In this example, the upper block (lines 20–24) specifies the molecules and molecule domains. Three molecules are incorporated: molecule A with one binding site named b1, molecule R with the binding site b1 and the two modification sites p1 and p2 and molecule B with binding site b1. The lower block (lines 32–48) contains the reaction rules with patterns on the left and right of the <-> -symbols and kinetic parameters at the end of each reaction rule. For a complete specification of BNGL see.