Extension of Simple Types

 My Name is Mike Zoratti, I am a Software Architect with Nortel. Over the
last year
we have been working on a Sun JCP to come up with standard interfaces for
OSS products.  The link below describes the initiative.

http://java.sun.com/products/oss/


The interfaces defined use standard EJB interfaces, but as well define XML
based interfaces.
Actually Nortel is a big supporter of XML based interfaces. I actually
worked on deriving
the XML interfaces based on the EJB interfaces. The mapping is almost always
1-1, the W3C did a very good job on the Schema Definition Language. One
instance
where the mapping is not 1-1 is in the use of Enumerations (i.e. Simple
Types).

The definition of a simpleType that defines a set of enumerations is as
follows:

<simpleType name="OrderState">
	<restriction base="string">
		<enumeration value="open"/>
		<enumeration value="open.not_running"/>
	 </restriction>
</simpleType>

We have a base schema that defines these enumeration types and obviously
element type-definitions
that are based on the enumeration types. The base schema can however be
derived (imported into a 
derived schema) and in some instances the base enumeration types may need to
be extended, the same
way complexTypes can be extended.  The problem is that I have not found
anyway
of extending a simpleType enumerations. The way enumerations are defined,
based on restriction,
I don't know if you would even want to change the language to allow
extension. There may be a way
of extending simpleTypes and if so I would appreciate you passing that
knowledge on to me. 

If there is not a way of extending enumerations, please read-on.

Since we are on a deadline to define the interfaces, I came up with a
recommendation in
dealing with extending enumerations. The below document contains the
enumeration section of a
XML Design Guideline we came up with. It is basically a work around and not
exactly a clean solution.
I would appreciate any comments, whether our guildeline is a recommended
practice in dealing with 
extension of simpleTypes.

I would greatly appreciate your comments


Mike Zoratti
Software Architect
Nortel Networks
Toronto, Ont
(416) 672-2727 X 4817

 <<XMLDesignGuildelinessubset.doc>>  <<XMLDesignGuildelinessubset.txt>>