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Optional elements in all groups

From: Martin Bryan <mtbryan@sgml.u-net.com>
Date: Tue, 7 Mar 2000 15:45:37 -0000
Message-ID: <000601bf886d$71d41340$0dc466c3@sgml>
To: <www-xml-schema-comments@w3.org>
The current (2000/02/25) restriction on all groups that all particles must
be present for the group to work will severely reduce the applicability of
all groups to be used for electronic business applications.

For electronic business we need to be able to say that an Information Set is
made up of one or more of the following set of Information Units. The basic
model for Information Sets is (a? & b? & c? & d? & e? ...). However XML
Schemas cannot describe such a model.

While the above model is not good for validation purposes (where you need
lists of valid elements) it should be possible to define complex types used
for element equivalence classes where the "extension" (or is it a
"restriction"?) requires that one or more of the elements has minOccurs set
to 1 prior to use.

The lack of repeatability of any element in an all group is also going to
give problems in the long term. While I understand the technical reason for
this I believe in the long term it will prove to be a significant problem
for the reusability of schema components, particularly equivalence classes.

Martin Bryan
Technical Manager, The Diffuse Project
The SGML Centre, 29 Oldbury Orchard, Churchdown, Glos GL3 2PU, UK
Phone/Fax: +44 1452 714029  E-mail: mtbryan@diffuse.org

For details of The SGML Centre visit http://www.sgml.u-net.com

For details of the EU-funded DIFFUSE project visit http://www.diffuse.org
Received on Tuesday, 7 March 2000 14:42:50 UTC

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