XSD Element Substitution

Through XML Schema, one element can substitute another element.

Element Substitution

Let's illustrate: Our users come from the UK and Norway. We want to give users the ability to choose whether to use Norwegian element names or English element names in XML documents.

To solve this problem, we can define asubstitutionGroup. First, we declare the main element, then we declare secondary elements, which can declare that they can substitute the main element.

In the above example, the "name" element is the main element, and the "navn" element can replace the "name" element.

Here is a fragment of an XML schema:

A valid XML document would look like this (according to the above schema):

Or like this:

Blocking Element Substitution

To prevent other elements from substituting a specified element, use the block attribute:

Here is a fragment of an XML schema:

A valid XML document should look like this (according to the above schema):

But the following document is no longer valid:

Using substitutionGroup

The type of the substitutable element must be the same as that of the main element, or derived from the main element. If the type of the substitutable element is the same as the main element's type, then you do not need to specify the type of the substitutable element.

Note that all elements (the main element and substitutable elements) in the substitutionGroup must be declared as global elements, otherwise it will not work!

What are Global Elements?

Global elements are direct children of the "schema" element! Local elements are elements nested within other elements.