As noted by Meng et al. , reaction related tasks operate on molecules. There are numerous machine readable molecular representations , including molecular graphs and strings, and in this work molecules are represented as SMILES strings. Each character m i in a SMILES string represents an atom or a molecular feature (bond, branch, ring closure): M := m 1 , m 2 , m 3 , . . . , m L , where L is the total number of characters in the string. Molecules can take on one of three roles in a reaction: reactant, product, or agent. A reaction R transforms N reactant molecules (sometimes called educts) Figure : Overview of ORDerly.