EPUBCheck is the official W3C conformance checker for EPUB publications. It validates EPUB 2 and EPUB 3 files against the respective specifications, including OCF packaging, OPF metadata, XHTML/SVG content, CSS, media overlays, navigation documents, and accessibility metadata. The tool operates as a Java command-line application and library, using a modular checker architecture where dedicated handlers validate specific resource types (e.g., OCFChecker, OPFChecker, OPSChecker, CSSChecker). Validation is driven by a combination of RelaxNG schemas for structural rules and Schematron for cross-cutting constraints. The project includes an extensive test suite using Cucumber/BDD features and thousands of test EPUB packages covering error and valid scenarios across all profile extensions (ePub 3, EDUPUB, dictionaries, indexes, multiple renditions, previews, and region-based navigation).
factur-x is a Python library for generating, validating, and extracting Factur-X/ZUGFeRD hybrid PDF+XML invoices. It exposes a high-level API (generate_from_file, generate_from_binary, get_xml_from_pdf, xml_check_xsd, xml_check_schematron, generate_cii_xml, generate_ubl_xml) and three CLI entry points (facturx-pdfgen, facturx-pdfextractxml, facturx-xmlcheck). The library supports both CII (Cross-Industry Invoice) and UBL 2.1 XML profiles, and bundles the necessary XSD schemas, Schematron/XSLT validation rules, and code-list databases. It is a standards-compliance tool for e-invoicing, not a data pipeline or research project.