Quality information is essential organizations' success and efficacy. Because of this crucial role of information, organizations spend part of their budget with information systems. Due to the great value of information, the user interface, the way in which users interact with software to perform their tasks, becomes an important part of systems. It is necessary to design user-friendly interfaces, that is, interfaces that are easy to use. To obtain such systems´ interfaces, the designers must take in consideration the non functional requirement (NFR) usability at the system definition. Failure to take NFRs in consideration has been reported in the literature. In this article we show how the lack of consideration of the NFR usability interferes on the quality of a product. We define the nonfunctional requirements and then analyze how some examples are used in a famous commercial Brazilian site, submarino.com. These requirements allow the designer to use facilities that improve the system's efficacy.
user interface design; information systems; non-functional requirements; usability
