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choice group particel whose {particles} is empty

From: Stanley Guan <stanley.guan@oracle.com>
Date: Wed, 25 Sep 2002 14:23:45 -0700
Message-ID: <012601c264d9$d4d0cdd0$c5b42382@us.oracle.com>
To: <xmlschema-dev@w3.org>
Cc: "Schema Interest Group" <w3c-xml-schema-ig@w3.org>
There is a difference between choice and {all, sequence} group particles 
in determining whether its {content type} is empty or whether a particle
is pointless:
   choice -- {particles} is empty plus its {min occurs} is 0
   {all, sequence} -- {particles} is empty

It looks to me that the following two groups are different:
   choice A -- its {minOccurs} = 0 and {particles} is empty
   choice B -- its {minOccurs} = 1 and {particles} is empty

For choice A, its {content type} is empty and it's 
pointless.  For choice B its {content type} is not
empty and it's not pointless because it defines a "negative
group particle" where no sequence (including empty sequence) of
element information items can be valid with respect to it.

Is this interpretation correct?


Received on Wednesday, 25 September 2002 17:30:08 UTC

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