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The IUPAC International Chemical Identifier
InChI 1.02beta Software Release,
A beta-release of InChI version 1.02 software was issued in September
2007. The complete package, downloadable from www.iupac.org/inchi/download/
contains the following
source code and Application Program Interface (API)
stand-alone executable (cInChI)
description of new features, with examples of using
copy of GNU LGPL licence
Full InChI documentation, Windows executable (wInChI.exe), and validation
set will be included in the final version 1.02 release.
The principal new features of this release are:
(1) A fixed-length (25-character) condensed digital representation
of the Identifier to be known as InChIKey. In particular, this will
facilitate web searching, previously complicated
by unpredictable breaking of InChI character strings by search engines
allow development of a web-based InChI lookup service
permit an InChI representation to be stored in fixed
make chemical structure database indexing easier
allow verification of InChI strings after network
An example of InChI with its InChKey equivalent is shown below. There
is a finite, but very small probability of finding two structures
with the same InChIKey. For duplication of only the first block of
14 characters this is 1.3% in 109,
equivalent to a single collision in one of 75 databases of 109
First block (14 letters), encodes molecular skeleton (connectivity):
Second block (8 letters), encodes proton positions (tautomers), stereochemistry,
isotopes, reconnected layer: UHFFFAOY
Flag character, indicates InChI version, presence/absence of fixed
H layer, isotopes, and stereochemistry: A
Check character: W
(2) Restructured InChI generating software that separates key steps
in its creation from an input chemical structure file. Among other
uses, this allows checking of intermediate results to enable easier
testing and development of InChI-based applications.
(3) Bug fixes designed to withstand malicious attempts to attack
a Web server by providing a specially designed InChI string input
to InChI binaries.
Users are encouraged to report their experiences and any problems
via the SourceForge website (http://sourceforge.net/projects/inchi).
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Page last modified 28 November 2007.
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