The MusicXML W3C XML Schema Definition (XSD) provides a stricter definition of the MusicXML 3.1 format than does the MusicXML Document Type Definition (DTD). MusicXML semantics that were previously only captured in the documentation are now enforced during schema validation.
The XSD improves the experience of MusicXML users by making MusicXML software more reliable. It also makes MusicXML easier to use with the latest XML technologies, including XQuery, XML databases, and XML code generators.
The MusicXML XSD is divided into several files, as listed here. The MusicXML file is the main file for partwise and timewise scores. The opus file represents collections of works. The xlink and xml files represent elements in the XLink and XML namespaces, respectively.
You can download all the MusicXML DTD and XSDs as a single zip file from the W3C GitHub repository:
You can also view the individual DTD files on GitHub:
These definitions do not contain a new version of the container or MIDI file DTDs. Please see the MusicXML 3.1 DTD index for the links to those files.