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RE: XML Schema Question: specifying restrictions for a list of

• To: 'Peter Loh Yoon Chao' <yoonchao@s...>, xml-dev@l...
• Subject: RE: XML Schema Question: specifying restrictions for a list of elements
• From: Tom Gaven <Tom.Gaven@e...>
• Date: Wed, 7 Apr 2004 08:51:59 -0400

Peter, I don't know if this can be done in XSD, but here is a RELAX NG
schema ( compact syntax ) that can handle it:

start  = computer_list
computer_list = element computer_list { computer*  &  computerDefault }
computer = element computer { computerNames }
computerDefault = element computer { attribute default { xsd:boolean },
computerNames }
computerNames =  'HP' | 'Dell' 

You can interleave ('&' connector) the single 'computer with default
attribute' with one or more 'computers without default attribute'.

Tom 

-----Original Message-----
From: Peter Loh Yoon Chao [mailto:yoonchao@s...] 
Sent: Wednesday, April 07, 2004 8:23 AM
To: xml-dev@l...
Subject:  XML Schema Question: specifying restrictions for a list
of elements


Hi,

I have the following construct in my XML document:

        <computer_list>
          <computer default="true">Dell</do_type>
          <computer>HP</do_type>
        </computer_list>

Only 1 of <computer> can have the "default" attribute set to true.  I am
trying to specify the corresponding XML schema to enforce this.  I tried the
following among other variations:

                    <xs:element name="computer_list">
                      <xs:complexType>
                        <xs:sequence>
                          <xs:element maxOccurs="unbounded" name="computer">
                            <xs:complexType>
                              <xs:simpleContent>
		        <xs:restriction base="xs:string">
		          <xs:enumeration value="Dell"/>
		          <xs:enumeration value="HP"/>
		        </xs:restriction>
                                <xs:extension base="xs:string">
                                  <xs:attribute name="default"
type="xs:boolean" use="optional" />
                                </xs:extension>
                              </xs:simpleContent>
                            </xs:complexType>
                          </xs:element>
                        </xs:sequence>
                      </xs:complexType>
                    </xs:element>

The above suffers from the following problems:
1.)  It allows the "default" attribute to be set to true for any number of
<computer>.
2.)  With the <xs:restriction> element, the parser complained that "Element
'extension' is invalid, misplaced, or occurs too often."

Would really appreciate any input as to the modifications required to
achieve my objectives.  Thanks.

Peter


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