Validation with lxmlValidation with lxml Apart from the built-in DTD support in parsers, lxml currently supports three schema languages: DTD, Relax NG and XML Schema. All three provide identical APIs in lxml, represented by validator classes with the obvious names. lxml also provides support for ISO-Schematron, based on the pure-XSLT skeleton implementation of Schematron: There is also basic support for pre-ISO-Schem
