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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?

Thx,

-Stanley
Received on Wednesday, 25 September 2002 17:30:08 GMT

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