Single point of Connection?
Major advantage of XI and other middleware technologies is ..
XI is a single point of connection.
What does it mean exactly with others?
it is possible to handle parallel messages in IE.but i guess you are looking for message processing in general.
see all the messages are processed in the order they arrived ,you have the option of prioritizing the messages in IE meaning you can give a higher priority to some important messages but this prioritizing is not possible at the adapter engine level,so adapter will pick the messages in the order they arrived,now when they enter IE and you have set the priority for them then they are processed based upon that,if no priority has been set they are processed in the order they were received