Compatibility between Balsa and ProtoSMILES is summarized in Table . Barring elements of ProtoSMILES that are either underspecified or internally inconsistent (entries marked "maybe"), Balsa can be seen to be a subset of Proto-SMILES. Output from Balsa writers should therefore be readable by SMILES readers. However, output from SMILES writers may or may not be readable by Balsa readers. Balsa can therefore be characterized as forward compatible with ProtoSMILES .