Schema Tutorial

Abstract type

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)