OWLXML

OWLXML, or the OWL XML serialization, is an XML-based syntax for serializing ontologies written in the Web Ontology Language (OWL). It provides a structured, machine-readable representation of OWL ontologies using XML elements and attributes to encode classes, properties, individuals, and axioms. OWLXML is one of the standard serializations defined for OWL 2, complementing RDF/XML, Turtle, and the Manchester and Functional-Style syntaxes. While RDF/XML and Turtle are widely used for data interchange on the Semantic Web, OWLXML emphasizes a direct mapping from OWL axioms to XML constructs, which can be convenient for programmatic processing in XML-centric pipelines.

Format and features: The syntax uses an OWL-specific XML vocabulary and a hierarchical document model, with elements representing ontology components (such as ontology, classes, properties, and individuals) and nested structures capturing axioms like SubClassOf, EquivalentClasses, DisjointClasses, property domain and range, and class membership of individuals. It supports imports, annotations, and datatype properties, among others. The XML representation tends to be verbose but is well suited for those who work with XML schemas and XSLT.

Usage and compatibility: OWLXML is supported by major ontology editors and reasoners and can be imported or exported by tools that implement the OWL 2 XML serialization. It is particularly useful in workflows that require XML validation, transformation, or integration with XML-based pipelines. Challenges include greater verbosity and less intuitive readability compared to some other syntaxes, which has limited its adoption for manual authoring.