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xmlxsdxsd-validationxml-validation

XSD unique constraint within sibling elements

I have the below XML file. I'm trying to create a unique constraint in the XML file so that the id of a book should be unique within the library. I tried creating one but was able to create a unique constraint within the group.

<library>
  <group>
    <groupName>Group 1</groupName>
    <books>
      <book>
        <name>Aa</name>
        <id>11</id>
      </book>
      <book>
        <name>Bb</name>
        <id>12</id>
      </book>
    </books>
  </group>
  <group>
    <groupName>Group 1</groupName>
    <books>
      <book>
        <name>Cc</name>
        <id>11</id>
      </book>
      <book>
        <name>Dd</name>
        <id>14</id>
      </book>
    </books>
  </group>
</library>

In the given file, Book Name 'Cc' has the id 11 which is the same as Book Name 'Aa' and hence the validation should fail. Please help me on where did I go wrong Here is my xsd file

<xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:element name="library">
    <xs:complexType>
      <xs:sequence>
        <xs:element maxOccurs="unbounded" name="group">
          <xs:complexType>
            <xs:sequence>
              <xs:element name="groupName" type="xs:string" />
              <xs:element name="books">
                <xs:complexType>
                  <xs:sequence>
                    <xs:element maxOccurs="unbounded" name="book">
                      <xs:complexType>
                        <xs:sequence>
                          <xs:element name="name" type="xs:string" />
                          <xs:element name="id" type="xs:unsignedByte" />
                        </xs:sequence>
                      </xs:complexType>
                    </xs:element>
                  </xs:sequence>
                </xs:complexType>
                <xs:unique name="uniqueRegAddr">
                  <xs:selector xpath="book"/>
                  <xs:field xpath="id"/>
                </xs:unique>
              </xs:element>
            </xs:sequence>
          </xs:complexType>
        </xs:element>
      </xs:sequence>
    </xs:complexType>
  </xs:element>
</xs:schema>
Solution

  • It's the library element that's invalid if there are two books with the same ID, so the uniqueness constraint needs to be defined for a library. You've defined a constraint on the validity of a books element, which is too narrow.