SMILES arbitrary target specification

SMILES arbitrary target specification (SMARTS) is a language for specifying substructural patterns in molecules. The SMARTS line notation is expressive and allows extremely precise and transparent substructural specification and atom typing.

SMARTS is related to the SMILES line notation that is used to encode molecular structures and like SMILES was originally developed by David Weininger and colleagues at The Pomona College Medicinal Chemistry Project (MedChem). A SMARTS software search engine named GENIE was used as an additional user-specified search filter in the MedChem database searching tool MERLIN. GENIE was also used in the MedChem interpreted language GCL (GENIE Control Language), where input was a list of structures. In GCL, a SMARTS specification was used as an expression that could be used in control flow statements. For example "for (SMARTS) {...}" would loop over each substructure (of the currently examined structure) that matched a SMARTS specification. Additional SMARTS development was made at Daylight Chemical Information Systems, Inc, which is a private company that was spun out of the software side of MedChem.

The most comprehensive descriptions of the SMARTS language can be found in Daylight's SMARTS theory manual,^[1] tutorial ^[2] and examples.^[3] OpenEye Scientific Software has developed their own version of SMARTS which differs from the original Daylight version in how the R descriptor (see cyclicity below) is defined.