Unlike other components EO’s almost always contain business data. Rule base data and control based "outputs" are almost always considered External Inquiries. This is true due to the fact that rule data and control type data is not derived (or derivable).

Notification Messages are considered EOs. A notification message differs from an error message. A notification message is an elementary process, while an error message (or confirmation message) is part of an elementary process. A notification message is the result of some business logic processing. For example, a trading application may notify a broker that the customer trying to place an order does not have adequate funds in their account.

Derived Data displayed in textual fashion (rows and columns) and graphical format is an example of two external outputs.