Transforms:

Use the new language, SMIRKS, which is a hybrid of a Reaction and a Reaction pattern. As a subset of SMARTS, all valid SMIRKS are valid reaction queries.

Additional requirements:

• must have unit stoichiometry,
• the atom map must account for every atom on both sides of reaction unambiguously,
• explicit hydrogens appear on both sides of transform and are mapped,
• atom expressions may be SMARTS for nodes whose bonding doesn't change, otherwise atom and bond expressions are SMILES.

A transform is 'applied' to a molecule or set of molecules. The result is a set of reactions, each of which has the given molecules as reactants and the molecules which result from the reaction as products. (Note that a transform can be applied in either direction).

Can be stored in databases (replace every SMARTS node expression by '*' to get a valid reaction).

In theory, transforms can be abstracted from sets of specific reaction instances (generalization).