Any type can be declared abstract by adding the 'abstract' attribute with a value of 'true'.

This means no element can be declared of that type.

The only exception is for substitution groups (next slide).

Example:

<xs:complexType name="Person" abstract="true">
<xs:sequence>
<xs:element name="name" type="my:PersonName"/>
</xs:sequence>
</xs:complexType>