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RE: Determinization in case of ambiguity or Should XML validators report on schemas that violate the UPA constraint?

From: Michael Kay <mike@saxonica.com>
Date: Tue, 17 Apr 2007 12:11:18 +0100
To: "'Shlomo Yona'" <S.Yona@F5.com>, "'Henry S. Thompson'" <ht@inf.ed.ac.uk>
Cc: <xmlschema-dev@w3.org>
Message-ID: <006a01c780e1$265833a0$a30f210a@turtle>

> I had another example where an xsd:sequence with an implied 
> minOccurs="1" and maxOccurs="1" contains particles with minOccurs="0".
> What is the expected behavior when none of these particles 
> appear in an XML instance?

It's quite valid to have a sequence with minOccurs="1" that contains an
element with minOccurs="0". Conceptually it means that the sequence must
occur, but if all the elements within the sequence are optional, then the
sequence is allowed to be empty. Of course in an instance document you can't
tell the difference between an empty sequence and an absent sequence, so you
might as well have written minOccurs="0" on the whole sequence, but in the
grammar they are subtly different.

Michael Kay
Received on Tuesday, 17 April 2007 11:11:52 UTC

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