Complex sentence: The Attentive User Interfaces (AUI) are User Interfaces that manage the user attention deciding when to interrupt the user, the kind of warnings, and the level of detail of the messages presented to the user.
Split into simpler sentences: The Attentive User Interfaces (AUI) are User Interfaces that manage the user attention. For instance an AUI can manage notification, deciding when to interrupt the user, the kind of warnings, and the level of detail of the messages presented to the user.