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XML schema allowing duplicate identifier with unique

I am trying to create an XML schema for books where a unique identifier is required for each book entry. However, it just doesn't work. Below is the XSD I am using,

<?xml version="1.0"?>

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
           elementFormDefault="qualified"
           attributeFormDefault="unqualified">

  <xs:element name="BookShelf">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="Description" type="xs:string" minOccurs="0"/>
        <xs:element name="Shelf" type="ShelfType" minOccurs="1" maxOccurs="10"/>
      </xs:sequence>
    </xs:complexType>
  </xs:element>

  <xs:complexType name="ShelfType">
    <xs:sequence>
      <xs:element ref="Book" minOccurs="0" maxOccurs="unbounded"/>
    </xs:sequence>
  </xs:complexType>


<xs:element name="Book">
  <xs:complexType>
    <xs:sequence>
      <xs:element name="Title" type="xs:token"/>
      <xs:element name="Language" type="xs:language"/>
    </xs:sequence>
    <xs:attribute name="id" type="xs:string" use="required"/>
  </xs:complexType>
  <xs:unique name="unique-bookId">
    <xs:selector xpath="Book"/>
    <xs:field xpath="@id"/>
  </xs:unique>
</xs:element>
</xs:schema>

The XML I'm trying to validate with this,

<?xml version="1.0"?>

<BookShelf>
    <Description>My bookshelf</Description>
    <Shelf>
        <Book id="1">
            <Title>Seitsemän veljestä</Title>
            <Language>fi</Language>
        </Book>
        <Book id="1">
            <Title>Another title</Title>
            <Language>en</Language>
        </Book>
    </Shelf>
</BookShelf>

which correctly checks, even if it should not (I used the same identifier for 2 entries). I'm new to XML and would appreciate it if someone could indicate what I'm doing wrong here?

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2 answers

<xs:unique> - -, Book , Book. ids , :

  <xs:element name="BookShelf">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="Description" type="xs:string" minOccurs="0"/>
        <xs:element name="Shelf" type="ShelfType" minOccurs="1" maxOccurs="10">
          <xs:unique name="unique-bookId">
            <xs:selector xpath="Book"/><!-- selects books on this shelf -->
            <xs:field xpath="@id"/>
          </xs:unique>
        </xs:element>
      </xs:sequence>
    </xs:complexType>
  </xs:element>

, , BookShelf :

  <xs:element name="BookShelf">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="Description" type="xs:string" minOccurs="0"/>
        <xs:element name="Shelf" type="ShelfType" minOccurs="1" maxOccurs="10"/>
      </xs:sequence>
    </xs:complexType>
    <xs:unique name="unique-bookId">
      <xs:selector xpath="Shelf/Book"/><!-- selects books on all shelves -->
      <xs:field xpath="@id"/>
    </xs:unique>
  </xs:element>

, , targetNamespace, , XPath " ". xmlns:tns="<target namespace URI>" xs:schema, tns:Shelf/tns:Book.

+10

? , xs:ID id xs:string:

<xs:attribute name="id" type="xs:ID" use="required"/>

, XML id. XML- , , , id-1.

+3

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