Chemical Markup Language - CML
XML is a mainstream approach providing semantics for science, such as MathML, SBML/BIOPAX (biology), GML and KML (geo) SVG (graphics) and NLM-DTD, ODT and OOXML (documents). CML provides support for most chemistry, especially molecules, compounds, reactions, spectra, crystals and computational chemistry (compchem).
CML has been developed by Peter Murray-Rust and Henry Rzepa since 1995. It is the de facto XML for chemistry, accepted by publishers and with more than 1 million lines of Open Source code supporting it. CML can be validated and built into authoring tools (for example the Chemistry Add-in for Microsoft Word). A list of CML-compliant and CML-aware software can be found on the software page.
There are several versions of the CML schema. The most recent schema is schema 3. This essentially relaxes many of the constraints imposed in the previous stable release (schema 2.4), allowing users to put together the elements and attributes in a more flexible manner to fit the data that they want to represent more easily.