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<title>Using xsi:type</title>
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<searchtitle>Using xsi:type</searchtitle>
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<shortdesc>If you have elements in your XML file whose type is a complex type,
xsi:type support in the XML editor lets you choose between the complex type
and any other complex types derived from it.</shortdesc>
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<context><p>The XML Schema specification allows you to derive types by extension.
For example, you have an XML schema and you create a complex type for it called
 <userinput>Address</userinput>. You then add some basic elements to <userinput>Address</userinput>,
such as <userinput>streetName</userinput> and <userinput>city</userinput>.</p><p>After
this, you derive (by extension) two new complex types from  <userinput>Address</userinput> - <userinput>USAddress</userinput> and <userinput>UKAddress</userinput
> You add a new element to <userinput>USAddress</userinput> called  <userinput>state</userinput>,
and also a new element to <userinput>UKAddress</userinput> called <userinput>postcode</userinput>.</p><p>After
you have done this, you create two more elements - <userinput>billTo</userinput> and <userinput>shipTo</userinput> -
as  <systemoutput>Address</systemoutput> types.</p><p>When you create an XML
instance document for an element such as  <systemoutput>billTo</systemoutput> or
 <userinput>Address</userinput>, an xsi:type attribute will automatically
be added to it. For example:</p><codeblock>&lt;billTo xsi:type="ipo:Address"></codeblock><p>The
xsi:type attribute is used to identify derived complex types (as well as complex
types that have been derived from).</p><p>In the Design view of the XML editor,
a list will be available, letting you select the appropriate type definition
(<uicontrol>Address</uicontrol>, <uicontrol>USAddress</uicontrol>, or  <uicontrol>UKAddress</uicontrol>).
The guided editing for the content model will reflect the type definition
that you choose. For example, if you select  <uicontrol>USAddress</uicontrol> ,
your <codeph>billTo</codeph> element can contain a <codeph>state</codeph> element,
but it cannot contain a <codeph>postcode</codeph> element.</p><p>The XML example
"Editing and validating XML files" demonstrates <b>xsi:type</b> support.</p><p>For
more information about xsi:type, refer to the <b>Using Derived Types in Instance
Documents</b> section in <xref format="html" href="http://www.w3.org/TR/xmlschema-0/#UseDerivInInstDocs"
scope="external">XML Schema Part 0: Primer.</xref></p><p>For more information
about validation semantics when xsi:type is used, refer to the <b>Schema-Related
Markup in Documents Being Validated</b> section in  <xref format="html" href="http://www.w3.org/TR/xmlschema-1/#xsi_type"
scope="external">XML Schema Part 1: Structures</xref> </p></context>
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