1. A method for mapping a tag in a markup language (ML) document to a class using namespaces, comprising: analyzing a tag in the ML document; referencing a definition file location attribute in the ML document, wherein the definition file location attribute is identified by the tag; retrieving a definition file from a storage location identified by the definition file location attribute, wherein the definition file includes: a schema that limits the scope of attributes in the definition file, a list of assemblies that references the definition file, a list of common language runtime namespaces associated with the list of assemblies that references the definition file, wherein each common language runtime namespace includes a list of common language classes associated with the common language runtime namespace, and an installation tag that includes a uniform resource identifier for installing assemblies of the list of assemblies; referencing a common language runtime namespace related to the tag within the definition file to determine the common language runtime class associated with the tag; and locating the common language runtime class in an assembly such that the tag is mapped to the common language runtime class.