"Open Enumerations"

[Rich Salz <rsalz@datapower.com>]

At the WS-I basic security profile face-to-face last week, there was 
some discussion about the fact that there are extension points in 
WS-Sec, with a few well-known QNAME and/or URI's.  For example, the 
Qname to use when sending a SOAP Fault, or the URI to use in the 
valueType attribute.

At that meeting, Martin Gudgin, or "gudge," mentioned a techique he's 
using in some of the other committees he's on.  (The list is daunting, 
and includes SOAP, WSDL, etc etc.  The man clearly has a cast-iron 
constitution.)  There had been some discussion of this on one of the 
other mailing lists, but since he's not on the WSS list, many folks here 
never saw it.  To cut to the chase, I'm forwarding one of the latest 
messages in that thread, which explains his "open enumeration" schema 
technique in detail.

At this point, I think it's just an "FYI" matter.  But it is a clever 
use of schema, and something to consider for future work.
	/r$
-- 
Rich Salz, Chief Security Architect
DataPower Technology                           http://www.datapower.com
XS40 XML Security Gateway   http://www.datapower.com/products/xs40.html
XML Security Overview  http://www.datapower.com/xmldev/xmlsecurity.html

--- Begin Message ---

• From: "Martin Gudgin" <mgudgin@microsoft.com>
• To: "Eve L. Maler" <Eve.Maler@Sun.COM>
• Date: Mon, 2 Feb 2004 08:51:20 -0800

OK, so here is the 'cute hack' ;-)

Assuming in scope ns decls for xs, tns and foo...

First, define your enumeration as normal:

 <xs:simpleType name='MyEnum' >
  <xs:restriction base='xs:QName' >
   <xs:enumeration value='foo:Val1' />
   <xs:enumeration value='foo:Val2' />
   <xs:enumeration value='foo:Val3' />
  </xs:restriction>
 </xs:simpleType>

Second, define a union of your enumerated type and the base ( in that
order ):

 <xs:simpleType name='MyOpenEnum' >
  <xs:union memberTypes='tns:MyEnum xs:QName' />
 </xs:simpleType>

Third, stir one part open enum with one part element or attribute decl:

 <xs:element name='MyData' type='tns:MyOpenEnum' />

Legal values for MyData element include the QNames defined in the MyEnum
and any other QName. 

Attached schema validates good1.xml, good2.xml, good3.xml and fails
bad1.xml

Gudge
 

> -----Original Message-----
> From: Eve L. Maler [mailto:Eve.Maler@Sun.COM] 
> Sent: 02 February 2004 16:38
> To: Martin Gudgin
> Cc: Paul Cotton; Christopher B Ferris; Rich Salz; Reid, 
> Irving; Peter Dapkus; DeMartini, Thomas; wss@lists.oasis-open.org
> Subject: Re: [wss] Critical ISSUE (RE: [wss-comment] 
> Enumerations of QName fault codes)
> 
> Yikes.  Mea culpa!  I hadn't noticed that the enumeration was 
> actually typed with QName; somehow I thought it was in the 
> string value space. 
> This would make the "cute hack" a worthwhile one, after all.
> 
> 	Eve
> 
> Martin Gudgin wrote:
> 
> > I don't understand
> > 
> > "still makes the wsse: prefix a unique first-class citizen"
> > 
> > Defining QNames in a schema enumeration fixes the URI and 
> Local Name 
> > parts, not the prefix part...
> > 
> > Gudge
> > 
> > P.S. I note that the WSS list is bouncing my posts ( understandably 
> > given I'm not on the TC ), could someone re-post as 
> appropriate? Thanks.
> 
> -- 
> Eve Maler                                        +1 781 442 3190
> Sun Microsystems                            cell +1 781 354 9441
> Web Products, Technologies, and Standards    eve.maler @ sun.com
> 
> 

openenum.xsd

<a:MyData  xmlns:a='http://example.org/types' >This is not a QName</a:MyData>
           

<a:MyData  xmlns:a='http://example.org/types' 
           xmlns:b='http://example.org/stuff' >b:Val2</a:MyData>

<a:MyData  xmlns:a='http://example.org/types' 
           xmlns:foo='http://example.org/stuff' >foo:Val3</a:MyData>

<a:MyData  xmlns:a='http://example.org/types' 
           xmlns:bar='http://example.org/otherstuff' >bar:SomeOtherName</a:MyData>

--- End Message ---