If this ComposableBody instance is a dynamic instance, uses this
ComposableBody instance as a starting point, create a builder
which can be used to create another ComposableBody instance
based on this one.
Sets the 'ack' attribute of the request to the value of the highest
'rid' of a request for which it has already received a response in the
case where it has also received all responses associated with lower
'rid' values.