{{Onesource, date=March 2009 Namespace-based Validation Dispatching Language (NVDL) is an

XML schema An XML schema is a description of a type of XML document, typically expressed in terms of constraints on the structure and content of documents of that type, above and beyond the basic syntactical constraints imposed by XML itself. These constra ...

language for validating XML documents that integrate with multiple

namespaces In computing, a namespace is a set of signs (''names'') that are used to identify and refer to objects of various kinds. A namespace ensures that all of a given set of objects have unique names so that they can be easily identified. Namespaces ...

. It is an ISO/

IEC The International Electrotechnical Commission (IEC; in French: ''Commission électrotechnique internationale'') is an international standards organization that prepares and publishes international standards for all electrical, electronic and r ...

standard, and it is Part 4 of the

DSDL Document Schema Definition Languages (DSDL) is a framework within which multiple validation tasks of different types can be applied to an XML document in order to achieve more complete validation results than just the application of a single tech ...

schema specification. Much of the work on NVDL is based on the older

Namespace Routing Language In its simplest form, a Namespace Routing Language (NRL) schema consists of a mapping from namespace URIs to schema URIs. An NRL schema is written in XML. DSDL Part 4 (ISO/IEC 19757-4), NVDL {{Onesource, date=March 2009 Namespace-based Validation ...

Validation

Most XML languages are based on a single XML namespace. The expectation in these cases is that XML elements in a particular namespace belong to that language, and elements in another namespace belong to another language. Many XML languages allow the use of arbitrary elements from other namespaces. The problem arises during the attempt to validate these hybrid documents. Each language is defined by a specific XML schema, but there is no linkage between the schemas. The purpose of NVDL is to provide that linkage, based on namespaces. By associating a schema validator with an NVDL schema, the validator can use multiple schemas to validate a single document, switching between them based on the namespaces used in that document.

Format

NVDL documents contain a list of rules, each of which has one or more actions to take when that rule is true. Rules include a specific namespace and a mode setting. NVDL recognizes the mode as a particular piece of state that changes as the document is processed. Actions occur when a rule is true. Actions can include validating a schema, declaring the instance document invalid, accepting this part of the instance document as valid, and continue validating as the parent did. Actions can also change the current NVDL mode. Multiple actions can be taken when a rule is true; this allows for validating a section of the instance document with multiple schemas of a different type.

Example

This NVDL schema will validate the parts that use the XHTML 1.0 namespace with a

RELAX NG In computing, RELAX NG (REgular LAnguage for XML Next Generation) is a schema language for XML—a RELAX NG schema specifies a pattern for the structure and content of an XML document. A RELAX NG schema is itself an XML document but RELAX NG also ...

schema, validate the parts that use the

SVG Scalable Vector Graphics (SVG) is an XML-based vector image format for defining two-dimensional graphics, having support for interactivity and animation. The SVG specification is an open standard developed by the World Wide Web Consortium s ...

1.0 namespace with a

Schematron Schematron is a rule-based validation language for making assertions about the presence or absence of patterns in XML trees. It is a structural schema language expressed in XML using a small number of elements and XPath. In many implementations ...

schema, and reject the document as invalid if it encounters elements with any other namespace.

External links

NVDL information

NVDL tutorial

ISO/IEC standards XML-based standards