<TransactedCancel> is an XSD element that has a child element <instanceId>. The XSD definition of the <TransactedCancel> element is as follows:

 <xs:element name="TransactedCancel">
       <xs:element minOccurs="0" name="instanceId"            
             xmlns:q4="http://schemas.microsoft.com/2003/10/Serialization/" type="q4:guid" />

instanceId: The value of this element is of type GUID and SHOULD match the identifier that is associated with the durable program instance in the Durable Program Instance Table on which this operation SHOULD be performed.