[standards-jig] schemas and sequence

Peter Saint-Andre stpeter at jabber.org
Mon Feb 17 14:27:26 UTC 2003

I have begun defining XML schemas for all existing Jabber protocols (in
fact I'm fairly far along: check out the 'protocol' project in CVS on
JabberStudio). The question immediately arises: are these schemas to be
construed as normative or descriptive? While I would like to be able to
define a set of normative schemas, I realize there may be some controversy
in this regard given the diversity of Jabber-based software out there in
the wild.

The main issue for me right now is the alternative of xs:choice versus
xs:sequence in defining the child elements of a parent. In the past, we
have not enforced any kind of sequence on child elements. However, in XML
schema it is possible to be much more precise regarding the number of
times a child element may be included if one uses xs:sequence rather than
xs:choice (or at least so it seems to me based on my knowledge of schemas
so far -- please correct me if I'm wrong). So xs:sequence seems like a
good thing if our schemas are descriptive; if they are normative, then
enforcing sequence may be problematic.

I'd appreciate hearing from implementers regarding this matter.



Peter Saint-Andre
Jabber Software Foundation

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