Overview
ISO/IEC 19757-4:2006 defines the Namespace-based Validation Dispatching Language (NVDL), part 4 of the Document Schema Definition Languages (DSDL) suite. NVDL provides a standardized way to dispatch elements and attributes of an XML document to different validators based on their XML namespaces. An NVDL script also declares which schemas those validators should use; those schemas may be written in any schema language (for example, RELAX NG, Schematron, W3C XML Schema), including other parts of ISO/IEC 19757.
Key Topics
- Namespace-based dispatching: Rules that route XML element/attribute sections to appropriate validators according to namespace.
- Schema binding: Specification of which schema(s) and schema language each dispatched section should be validated against.
- Data model and semantics: A document infoset abstraction and a formal semantics described in staged processing (creation of sections, constructing interpretations, combining/filtering, and validation).
- Syntax variants: Full and simple syntaxes for NVDL scripts; Annexes provide definitions using RELAX NG.
- Primitive operations and constructs: Core operations used to manipulate element/attribute sections and to express rules (e.g., allow/reject/validate/attach - listed in the standard’s syntax and simplification clauses).
- Conformance and examples: Conformance requirements for NVDL dispatchers and informative examples (e.g., RDF in XHTML, XHTML+XForms) to demonstrate practical use.
Applications
- Validate XML documents that mix multiple vocabularies (mixed namespaces) by dispatching parts of a document to different schema validators.
- Integrate heterogeneous schema languages in a single validation workflow (e.g., RELAX NG for structural checks and Schematron for rule-based checks).
- Build modular validation pipelines for complex content such as XHTML with embedded RDF, application profiles, or document compositions from different sources.
- Create validation tools, XML processing libraries, or enterprise validation services that need standardized namespace-aware dispatching logic.
Who Should Use This Standard
- XML tool and validator developers implementing namespace-aware validation dispatch.
- Schema authors and integrators working with mixed-namespace XML documents.
- Systems architects and software engineers building document processing or content validation pipelines.
- Standards bodies and organizations needing interoperable validation frameworks across schema languages.
Related Standards
- ISO/IEC 19757 (DSDL) - Part 1 (Overview), Part 2 (RELAX NG), Part 3 (Schematron) - useful when combining schema languages with NVDL.
- RELAX NG - often used in NVDL script syntax examples and annexes.
Keywords: ISO/IEC 19757-4:2006, NVDL, Namespace-based Validation Dispatching Language, DSDL, XML validation, schema languages, RELAX NG, Schematron, namespace dispatching.
Open preview (PDF)Information technology — Document Schema Definition Languages (DSDL) — Part 4: Namespace-based Validation Dispatching Language (NVDL)
