XML and XSD - use element name as replacement of xsi:type for polymorphism

Question

Taking the W3C vehicle XSD as an example:

Answer 1

There is a common design pattern around this, you can use sub-types (as you are already doing), and elements in a substitution group. Elements in the substitution group have to be of a sub-type of the element they are substituted for.

Unfortuntaly, substitution group elements need to be defined as global elements. So you would have this:

<complexType name="MeansOfTravel">
  <complexContent>
    <sequence>        
      <element ref="transport"/>
    </sequence>
  </complexContent>
</complexType>

<element name="transport" type="target:Vehicle"/>
<element name="plane" type="target:Plane" substitutionGroup="target:transport"/>

Then, in your XML document you can use:

<meansOfTravel>
    <plane>...</plane>
</meansOfTravel>

More info on substitution groups here. And no, unfortunately the parser cannot guess this, so you still have to list the elements :( There is one advantage over a choice though: the schema can be extended externally, by importing it, without modifying it. The choice could not be extended.