Namespace-based Validation Dispatching Language
The Namespace -based Validation Dispatching Language ( NVDL ) is an XML schema language for validating XML documents, whose structure was defined with different schema languages and in different namespaces. NVDL is an ISO / IEC standard, and part of the 4 DSDL specification. A large part of NVDL based on the developed by James Clark Namespace Routing Language ( NRL). In its simplest form, a NVDL document of a mapping from XML namespace URIs to schema URIs.
Validation
XML applications may contain elements or attributes from other XML applications. Often this is the namespace of the external XML application imports. One example is SVG within XHTML. The imported items are not necessarily defined in the same schema language like the imported XML application, creating a validation with only one schema language is not sufficient.
NVDL is based on namespaces, a connection between the different schemas and schema languages forth by assigning individual namespaces a schema. A validation software can be used to check on a specific XML document against different schemas.
Format
NVDL documents contain a list of rules that trigger different actions. Rules refer to a namespace and a mode. A mode is a specific state during the validation of the document. Different modes allow for example a strict and a lax validation.
Actions are executed when a rule matches. Actions can validate documents parts, explain the XML document to be invalid, declare a part of the document to be valid, the return processing to the parent node or change the current processing mode. Within a rule, different actions are allowed, for example, to check a single item against schemas in different schema languages .
Example