File: Data.xml
<?xml version="1.0"?>
<Books xmlns="http://www.wbex.ru"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.wbex.ru Schema.xsd">
<Book>
<Title>title 1</Title>
<Author>author 1</Author>
<Date>1998</Date>
<Publisher>publisher 1</Publisher>
</Book>
<Book>
<Title>title 2</Title>
<Author>author 2</Author>
<Date>1977</Date>
<ISBN>2-222-22222-2</ISBN>
<Publisher>publisher 2</Publisher>
</Book>
</Books>
File: Schema.xsd
<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.wbex.ru"
xmlns="http://www.wbex.ru"
xmlns:bk="http://www.wbex.ru"
elementFormDefault="qualified">
<xsd:element name="Books">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Book" maxOccurs="unbounded">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Title" type="xsd:string"/>
<xsd:element name="Author" type="xsd:string"/>
<xsd:element name="Date" type="xsd:string"/>
<xsd:element name="ISBN" type="xsd:string" minOccurs="0"/>
<xsd:element name="Publisher" type="xsd:string"/>
</xsd:sequence>
</xsd:complexType>
</xsd:element>
</xsd:sequence>
</xsd:complexType>
<xsd:unique name="UNIQ">
<xsd:selector xpath="bk:Book"/>
<xsd:field xpath="bk:ISBN"/>
</xsd:unique>
</xsd:element>
</xsd:schema>