The installer creates all necessary settings for Schematron validation on installing XML ValidatorBuddy. So Schematron validation runs out-of-the-box using the Saxon HE transformation engine (which is also installed). XML ValidatorBuddy provides Schematron validation by applying XSL transformations to the XML instance file. The required stylesheets are installed by the installer and located in the installation folder. It is possible to change those stylesheets or to use completely different ones if necessary. The paths to the XSL files and other settings are accessible on the "Schematron" page of the Options dialog. Schematron settings product screenshot Schematron Processing Instruction If the Schematron Processing Instruction is found in an XML instance document on doing Schematron validation the referenced Schematron schema file is used for validation. The File Explorer view in XML ValidatorBuddy also displays the text value of this PI, which should be a path to the Schematron schema. This way you can validate XML documents against any Schematron schema without the need to manually select the schema file. Simply select the documents with a valid Processing Instruction in the File Explorer window and use the "Validate with Schematron" command from the XML menu.