Schema Tutorial

Abstract type

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1. XML Schema

The schema below defines an abstract complexType named "myAbstractType" (attribute "abstract" is set to "true"). The type "AAA" is an extension of this type - we add the requirement that attribute "bbb" must be present. Element declaration cannot use abstract type.

Valid document

<root xsi:noNamespaceSchemaLocation="correct_0.xsd" bbb="1" xmlns="" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" >
<XXX>sdkhlg nkd</XXX>
</root>

Invalid document
This document is not valid, because the attribute "bbb" is missing.

<root xsi:noNamespaceSchemaLocation="correct_0.xsd" xmlns="" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" >
<XXX>sdkhlg nkd</XXX>
</root>

Correct XML Schema (correct_0.xsd)

<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema" >

  <xsd:element name="root" type="AAA"/>

  <xsd:complexType name="myAbstractType" abstract="true">
    <xsd:sequence minOccurs="1">
      <xsd:element name="XXX" type="xsd:string"/>
    </xsd:sequence>
  </xsd:complexType>

  <xsd:complexType name="AAA">
    <xsd:complexContent>
      <xsd:extension base="myAbstractType">
        <xsd:attribute name="bbb" type="xsd:string" use="required"/>
      </xsd:extension>
    </xsd:complexContent>
  </xsd:complexType>
</xsd:schema>

2. Relax NG

Although Relax NG does not contain such features, we can achieve the same effect with the Relax NG schema below.

Valid document

<root bbb="1" xmlns="">
<XXX>sdkhlg nkd</XXX>
</root>

Invalid document
This document is not valid, because the attribute "bbb" is missing.

<root xmlns="">
<XXX>sdkhlg nkd</XXX>
</root>

Correct Relax NG schema (correctRelax_0.rng)