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6.1 Element based Extensibility

WSDL 2.0 allows extensions to be defined in terms of element information items. 
The WSDL 2.0 schema defines a base type for use by extension elements.  (see Example 6-1 shows the type definition). The use of this type as a base type is, however, optional. 

Extension elements are commonly used to specify some technology-specific binding. They allow innovation in the area of network and message protocols without having to revise the base WSDL 2.0 specification. WSDL 2.0 recommends that specifications defining such protocols also define any necessary WSDL 2.0 extensions used to describe those protocols or formats. 

Example 6-1. Base type for extension elements
<xs:complexType name='ExtensionElement' abstract='true' >
  <xs:attribute ref='wsdl:required' use='optional' />
</xs:complexType>
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Move the example before the last paragraph.