Schema questions

[Mike Douglass <douglm@rpi.edu>]

Removing the substitutionGroup for components was relatively painless.

For properties it will be different:

I tried replacing the simple array of properties which used 
substitutionGroup to something like

<xs:complexType name="ArrayOfEventContainedProperties">
<xs:sequence>
<xs:choice minOccurs="0" maxOccurs="unbounded">
<!-- Exactly once -->
<xs:element ref="xcal:dtstamp"/>
<xs:element ref="xcal:uid"/>
...
<!-- 0 or more occurrences -->
<xs:element ref="xcal:attach"/>
...
<xs:element ref="xcal:resources"/>
<xs:element ref="xcal:rdate"/>
</xs:choice>
</xs:sequence>
</xs:complexType>

This still doesn't define how many times an element may occur and it has 
the undesirable characteristic (in Java anyway) that the resulting class 
is List<Object>.

However, it does have at least one good characteristic - the elements 
may appear in any order which is typically what happens. Also, when 
using the generated classes it is possible to iterate over the list of 
properties rather than name each one explicitly.

It would be possible to remove the choice and simply list each element 
with a minOccurs/maxOccurs. Now we've imposed ordering which may be an 
issue. Also we cannot express all the possibilities for some of the 
elements. For example there are various valid combinations of 
dtstart/end/duration which depend on semantics that cannot be expressed 
in the schema.




--

Mike Douglass                           douglm@rpi.edu
Senior Systems Programmer
Communication&  Collaboration Technologies      518 276 6780(voice) 2809
(fax)
Rensselaer Polytechnic Institute 110 8th Street, Troy, NY 12180