This section describes the XSchema document syntax. The XSchema document is an XML document containing a single XSchema element in which information describing the schema is nested. The XSchema element must be preceded by an XML declaration and may be preceded by other declarations, comments, and processing instructions.
The XSchema element is the root element for all XSchema documents. The declaration for the XSchema element is:
<!ELEMENT XSC:XSchema (XSC:Doc?, XSC:More?, XSC:Namespace?, (XSC:ElementDecl | XSC:AttDef | XSC:Choice | XSC:Sequence | XSC:Mixed | XSC:Ref | XSC:Notation | XSC:XSchema)*)>
Version CDATA #FIXED "1.0"
MimeType CDATA "application/xml"
FileExtension CDATA "xml"
id ID #IMPLIED>
The XSC:XSchema element contains other elements describing the XSchema and building a schema. These elements are described in later sections of this specification. The XSC:XSchema element may also contain other XSC:XSchema elements nested inside of it. This nesting of XSC:XSchema elements improves reusability of XSchemas by allowing the combination of multiple XSchemas inside of a single XSchema framework. It also allows finer-grained control over documentation for subsections of an XSchema.
The XSC:XSchema element's attributes include information about the version of the XSchema specification used as well as information about the type of documents described by the XSchema.
Information about the XSchema specification version used to create this XSchema, contained in the XSC:Version attribute, is critical to proper handling of documents should the specification be updated in the future. This specification is identified as version 1.0. Future major and minor versions of the XSchema specification should identify themselves differently. No provision is made at this time for nesting XSchemas using different versions of the specification under a parent XSchema element.
The XSC:MimeType and XSC:FileExtension attributes are used to provide a suggested MIME (Multipurpose Internet Mail Extensions) Content-type and file extension for documents created using a particular XSchema. Applications may use this information to identify XML document types. A document library that generates XML documents dynamically could assign file extensions and MIME types based on the XSchema used.
Applications using this information should use the values stored in the first XSchema encountered during processing. For instance, if an XSchema includes another nested XSchema, the values for the XSC:MimeType and XSC:FileExtension attributes of the root XSchema should be used.
By default, most XML documents are assumed to have a MIME type of application/xml, as described in "XML Media Types" by E.J. Whitehead and Murata Makoto. Developers who need different MIME types for documents created using particular XSchemas may register other MIME types with the IETF, as described in RFC 1590, or use the 'x-' prefix syntax for subtypes, as described in RFC 1521.