User interface engineering

User interface engineering is the engineering of the user interface. It addresses the need to develop interfaces that make users more productive. It is often considered as one of the more practical aspects of the field of human-computer interaction. Concerns include

standards
simplicity
utility
coherence
usability testing

Techniques for engineering user interfaces include

personas
paper prototypes
talk aloud protocol

References:

About Face by Alan Cooper.
Usability Engineering by Jakob Nielsen

User interface engineering is closely related to or a subset of software engineering.