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XML Namespaces

Visual Studio .NET 2003

XML namespaces provide a method for uniqueness, which differentiates between multiple schema authors who use the same element names. Namespaces qualify the names of XML elements and XML attributes in XML document instances. A qualified name consists of a prefix and a local name, separated by a colon. The prefix functions only as a placeholder; it is mapped to a Uniform Resource Identifier (URI) that specifies a namespace. The combination of the universally managed URI namespace and the local name produces a name that should be universally unique.

Namespaces in XML must conform to the World Wide Web Consortium (WC3) specification called Namespaces in XML. For more information, see the W3C spec on Namespaces on the W3C Web site (

By default in Visual Studio each of the elements in a schema has a prefix xs: which is associated with the XML Schema namespace through the declaration, xmlns:xs="", that appears in the schema element. The prefix xs: is used by convention to denote the XML Schema namespace, although any prefix can be used. The same prefix, and hence the same association, also appears on the names of built-in simple types — for example, xs:string. The purpose of the association is to identify the elements and simple types as belonging to the vocabulary of the XML Schema language rather than the vocabulary of the schema author.

See Also

XML Schemas and the XML Designer| XML Elements, Attributes, and Types | Changing the Target Namespace | Creating XML Schemas and Datasets | Relational Data in XML Schemas | XML Files