Types Revisited

As with many object-oriented programming languages, it is possible to define a type as being abstract using XML Schemas. This is accomplished using the boolean abstract attribute on the type definition. Given the following schema

<schema xmlns='http://www.w3.org/1999/XMLSchema'
        targetNamespace='http://flowers.org'
        xmlns:tns='http://flowers.org' >
  <complexType name='flower' abstract='1' />
  <element name='bouquet' type='tns:flower' />
</schema>

the bouquet element declaration refers to an abstract type. This means that one must provide a derived type in order to use the bouquet element in an instance document. When an element declaration refers to an abstract type, all instances of that element must use the xsi:type attribute ...

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