2.0 XSchema Syntax

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.

2.1 The XSchema Element

The XSchema element is the root element for all XSchema documents. The declaration for the XSchema element is:

<!ELEMENT XSC:XSchema (Doc?, (ElementDecl | Entity | Notation | Namespace | XSchema)*)>

<!ATTLIST XSC:XSchema
    XSC:Version CDATA #FIXED "1.0"
    XSC:MimeType CDATA "application/xml"
    XSC:FileExtension CDATA "xml">

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.

The XSC:XSchema element's attributes include information about the version of XSchema used as well as information about the type of documents created using the XSchema.

XSchema version information, 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 XSchema should identify themselves differently. No provision is made at this time for nesting XSchemas of different versions 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.