Simplified Molecular Input Line Entry System (SMILES) was first described by Weininger in 1988 . As a line notation , SMILES represents molecules as single line character sequences, or strings. SMILES has since been widely adopted. Read and write functionalities are routinely supported by popular cheminformatics toolkits, including: Open Babel ; RDKit ; Chemistry Development Kit ; JChem Base ; the Daylight Toolkit ; and OEChem TK . SMILES encodings can be found in many public-facing databases, including: PubChem ; ChEBI ; ZINC ; ChEMBL ; and Wikipedia . Raw SMILES strings have been used extensively in machine learning applications . Algorithmic selection of a single SMILES encoding has been used for molecular identification . SMILES has also been extended to carry various forms of metadata, as exemplified by Jmol SMILES , CurleySMILES , BigSMILES , and CXSMILES .