XSchema Spec - XSchema Element (Sections 2.0 and 2.1), Draft 5

[Simon St.Laurent]

Here is Draft 5 of the XSchema Element section.  I'm hoping that this is close 
to final and may be used shortly as part of the complete section 2 for review.

I made XSC:Namespace optional (minor glitch), added a lot of possible 
sub-elements to XSC:XSchema as requested by a number of writers on this list, 
and added a bit more explanation of why nesting XSchemas might be a good idea.

As always, a prettier HTML version of this will be posted shortly at 
http://purl.oclc.org/NET/xschema.

Simon St.Laurent
Dynamic HTML: A Primer / XML: A Primer / Cookies

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 (XSC:Doc?, XSC:More?, XSC:Namespace?, (XSC:ElementDecl | 
XSC:AttDef | XSC:Choice | XSC:Sequence | XSC:Mixed | XSC:Ref | XSC:Notation | 
XSC:XSchema)*)>

<!ATTLIST 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.


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