Kolab XML Format: Proposal for an XSD friendly update

Tobias Koenig tobias.koenig at kdab.com
Wed Oct 19 10:19:42 CEST 2011

On Tuesday 18 October 2011 18:46:24 Christian Mollekopf wrote:
> Hi,

> === Preserving of undefined tags ===
> Preserving unknown tags is far from trivial and a rather big
> development effort. I understand the use of an extensible format as it
> makes it very easy for vendors to implement their own special features
> using extensions (aka unknown tags). Also the idea that old clients can
> still make use of a subset of the data of
> newer versions of the format is intriguing. However I think there are a
> couple of severe drawbacks which make me think unknown tags are not a
> good idea after all.
While XML schema supports the definition of undefined child elements/attributes
on an element (see <any>), the autogenerated parsing/assembling code might not
be able to handle them... However that's more a technical problem (that can be 
solved) than a design problem.

> === Undefined order of elements ===
> This is mainly a technical problem for XSD. It is not feasible to
> implement an XSD Schema with an undefined order of the elements.
If the number of child elements is fixed, the <all> tag can be used instead of 
<sequence>, so this specific case of undefined order is supported by XML schema.

But require a order of elements in the kolab format sounds like a good idea 

> === No defined namespace ===
> Because the current format lacks a namespace it is not suitable to be
> used together with other XML technologies such as XSLT. The lack of a
> namespace increases the chance of nameconflicts with other formats such
> as ICAL. The design with a namespace is also more robust should we once
> want to extend the format.
ACK. Please use namespaces in the kolab format.

Tobias Koenig | tobias.koenig at kdab.com | Developer
KDAB (Deutschland) GmbH&Co KG, a KDAB Group company
Tel. Germany +49-30-521325470, Sweden (HQ) +46-563-540090
KDAB - Qt Experts - Platform-independent software solutions
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