A wildcard element represents an element that does not appear in the message model, but which could appear at the same position as the wildcard element in the message.
Wildcard elements provide a means of adding flexibility to the message model, so that messages can be parsed even if they do not exactly match the message model.
Wildcard elements can only appear within a complex type or group with Composition of sequence and Content Validation of closed. Wildcard elements provide a similar capability to setting the Content Validation property of a complex type or group to Open or Open Defined.
If the broker is prior to WebSphere Message Broker Version 6.0, the number of elements permitted to match against the wildcard element is unpredictable (Min Occurs and Max Occurs are ignored).