schemaxsd

SchemaXSD is a schema description language and validation framework designed for XML documents. It provides an alternative or complementary approach to the W3C XML Schema (XSD) by allowing developers to define the structure, constraints, and data types of XML data in a dedicated SchemaXSD notation. Schemas written in SchemaXSD can be used to validate XML instances and guide data interchange, transformation, and storage.

SchemaXSD emphasizes modularity and reuse. Its syntax supports modular schemas, imports, and includes, enabling components to be composed into larger definitions. Data types cover a core set compatible with common XML Schema types, plus extended constraints such as conditional validation, cross-element references, and default values. Validation is performed by a SchemaXSD processor that can operate in strict mode or with relaxed rules for legacy documents. The framework supports tooling for editors, schema testing, and error reporting.

Although SchemaXSD is distinct from XSD, many implementations provide conversion utilities to generate standard XSD from SchemaXSD definitions, or to validate XML documents against either schema form. The approach aims to integrate with existing XML namespaces and tooling, enabling gradual adoption in projects with complex domain models.

SchemaXSD is described in open documentation and community discussions. It remains a niche specification with limited formal standardization, but it has influenced schema design discussions by highlighting modularity and explicit constraint expression in XML schemas.

Related topics include XML Schema Definition (XSD), RELAX NG, and Schematron.