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Re: xs:group/xs:choice[@minOccurs | @maxOccurs]

• To: Bob Foster <bob@o...>
• Subject: Re: xs:group/xs:choice[@minOccurs | @maxOccurs]
• From: ht@i... (Henry S. Thompson)
• Date: Sat, 26 Jun 2004 11:01:31 +0100
• Cc: xml-dev@l...
• In-reply-to: <40DD24FF.2090806@o...> (Bob Foster's message of "Sat, 26Jun 2004 02:25:51 -0500")
• References: <000a01c45ae9$56a6fa80$6d61a485@ichiran><40DD24FF.2090806@o...>
• User-agent: Gnus/5.1006 (Gnus v5.10.6) XEmacs/21.4 (Security ThroughObscurity, linux)

Bob Foster <bob@o...> writes:

> I'm a bit puzzled by this. I can see why he can't have a
> minOccurs/maxOccurs on the group item as specified but why not on the
> choice nested in the group. This looks legal to me and I am curious
> what processors do not accept it.

On balance the reasoning the XML Schema WG went with was roughly this:

 1) Named model groups will be most useful if different references to
    them can have different min/max values;
 2) Allowing min/max on both references _and_ on the top level group
    in the named group definition, e.g.

       . . .
       <xs:group ref="myGroup" minOccurs="1" maxOccurs="10"/>
       . . .

    <xs:group name="myGroup">
     <xs:choice minOccurs="2" maxOccurs="4">
       . . .
     </xs:choice>
    </xs:group>

    would be _very_ confusing and difficult to explain;
 3) So we rule out min/max on the top group in a named model group defn.

Note also that

     <xs:choice minOccurs="0" maxOccurs="unbounded">
       <xs:element name="e1"/>
       <xs:element name="e2"/>
       <xs:element name="e3"/>
     </xs:choice>
 
means something _quite_ different from

     <xs:choice>
       <xs:element name="e1" minOccurs="0" maxOccurs="unbounded"/>
       <xs:element name="e2" minOccurs="0" maxOccurs="unbounded"/>
       <xs:element name="e3" minOccurs="0" maxOccurs="unbounded"/>
     </xs:choice>

For example, the first allows e1 e2 e1

The second does not.

ht
-- 
 Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
                     Half-time member of W3C Team
    2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440
            Fax: (44) 131 650-4587, e-mail: ht@i...
                   URL: http://www.ltg.ed.ac.uk/~ht/
[mail really from me _always_ has this .sig -- mail without it is forged spam]

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    • From: "Takuki Kamiya" <tkamiya@u...>
  • Re: xs:group/xs:choice[@minOccurs | @maxOccurs]
    • From: Bob Foster <bob@o...>

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