RE: [xml-dev] Creating a "General MusicXML" format using W3C XML Schemas

["Michael Kay" <mike@saxonica.com>]

> We would most likely use the W3C XML Schema format to define 
> these profiles. This is due to its extensive software 
> support, including pervasive parser support, comprehensive 
> tool support, and integration into other XML technologies 
> like JAXB and XQuery.

In general I think this is a good idea. However, the devil is in the detail.
Some XML vocabularies lend themselves well to being described using XML
Schema, others don't. The kind of things that tend to make it difficult are
use of microsyntax within element and attribute values, rules where the
structure depends on the content, and some forms of extensibility provision.

In theory you should be able to define a schema for each of your profiles.
XHTML attempts to do something similar. In practice it can be quite
difficult to manage schema variants like this without making them "cut and
paste" copies of each other. One technique I have used successfully is to
have a common baseline schema with private markup to indicate "this part of
the schema is present in variants A, B, and F", coupled with XSLT
transformations to generate the profile schema documents from this common
source.

Along with having a schema, another thing that can improve the accessibility
of instance documents is an XSLT or XQuery function library: in effect this
can encapsulate the data behind an object-oriented API, hiding details that
applications don't need to see.

Michael Kay
http://www.saxonica.com/