Complex types contain other element definitions and describe which children an element can contain. Complex types can contain both children and attributes.

The following example is from the OTA Low Fare Search request. The POS element has the POS_Type, which is a complex type that describes what the POS element can contain. The POS_Type contains Source, which is a child element. The Source element also has a complex type that also contains children and attributes.

To see the children, attributes, and constraints that exist for these elements and types, click the links.