The JATS4R Validator tool is a handy way for you to check your XML against JATS4R recommendations. For those interested, it uses XML Schematron rules to check the XML and flag any discrepancies with the recommendations. If you are interested in finding out more about Schematron rules and how they work, see this article in the JATS4R learning center.
Validator tool history
The validator was created by Alf Eaton (Coko Foundation) and has been worked on by Jeff Beck and Chris Maloney (NCBI). Currently the validator is maintained and enhanced by Alexander Powell (Cambridge University Press) and Chris Wilkinson (eLife) and overseen by Mike Eden (JATS4R Steering Committee, Cambridge University Press).
The code is maintained on the JATS4R Github repository and is open source.