RE: Open Content Model

Almost all schema elements support attribute extensibility. I couldn't even
tell you which ones don't without digging in the schema for schemas, and I
couldn't tell you why they were excluded. The annotation feature was not to
allow an open content model, but to allow both machine and human targetted
annotations to the schema. As far as a general open content model for
elements, no one as I recall ever requested such a feature, so it isn't
there. It might be something you or Allen Brown might want to bring up for
future versions.

David Cleary

  -----Original Message-----
  From: www-ws-desc-request@w3.org [mailto:www-ws-desc-request@w3.org]On
Behalf Of Jonathan Marsh
  Sent: Tuesday, April 23, 2002 12:43 PM
  To: www-ws-desc@w3.org
  Subject: RE: Open Content Model


  XSLT also has an essentially open content model, which has proved both
useful and harmless.



  On the other hand, XML Schema does not provide such an open content model.
As far as I can tell, it only allows attribute extensibility on a few
elements, and limits element extensibility to the <xs:annotation> element.
Personally, I never understood this decision.  It appears overly complex and
cumbersome.  Does anyone have any knowledge of the rationale for this
design?



  -----Original Message-----
  From: Keith Ballinger [mailto:keithba@microsoft.com]
  Sent: Monday, April 22, 2002 7:07 PM
  To: www-ws-desc@w3.org
  Subject: Open Content Model



  One item I've had on my plate is to describe why the open content model is
something we should try to take advantage of as much as possible with the
WDSL revision.



  To begin with, when I say open content model, I mostly mean allowing extra
element and attributes from other namespaces within a schema. This is
typically done with the <any/> and <anyAttribute/> schema tags. These
elements also allow you to specify which namespace (including ##other, which
means any namespace but the one in the schema), as well as the default
processing of these elements. An example of this can be found with the
<binding> element in WSDL today. This element allows child elements of the
type: <any namespace="##other" minOccurs="0" maxOccurs="unbounded" />



  Working with SOAP and WSDL over the past few years has shown me the value
in allowing this open content model. It is very useful especially for
extending a specification in new ways. As authors of specs, we may cover
many use cases and requirements in a first class way, but we need to provide
for those other requirements that come to us that we don't anticipate. The
open content model allows us to handle many of these.



  I would also recommend that we keep WSDLs mustUnderstand feature for
extensions, the wsdl:required attribute.



  As a matter of technique, I feel that we should be overly open as opposed
to overly closed. This would lead to putting this open content model on all
elements, and then finding reasons why it shouldn't be on one.



  Cheers,

  Keith