Schematron Schematron is another recent schema language. Schematron defines a set of rules and checks that are applied to an XML instance. Schematron takes a unique approach to schemas in that it focuses on validating document instances instead of declaring a schema. Schematron uses the XPATH syntax to define a series of rules that should or should not be true about a XML documents structure. You can choose to have elements and attributes validate based on conditions involving anything anywhere else in the document. Schematron has the appearance of an XSLT stylesheet and can be fully implemented by way of XSLT. Schematron also has existing perl modules available. However Schematron does lack any kind of built in data typing.