atomic connectivity molecular structure encoding format specification InChI format specification The IUPAC International Chemical Identifier (InChI) is a textual identifier for chemical substances, designed to provide a standard and human-readable way to encode molecular information and to facilitate the search for such information in databases and on the web. Developed by IUPAC and NIST during 2000-2005, the format and algorithms are non-proprietary and the software is freely available under the open source LGPL license (though the term "InChI" is a trademark of IUPAC). [source: Wikipedia, http://en.wikipedia.org/wiki/International_Chemical_Identifier]