Usability is an important aspect of product development that deals with the quality of

interaction between the user and the product. Capturing requirements is aimed at

understanding what the users expect the system to do. This report attempts to apply

principles from both the Usability Engineering and the Requirements Engineering

methodologies in the development of a subsystem for managing an e-commerce solution.

The main focus is on the user interface design, which is developed by iterating the three

phases of design, usability testing and evaluation, until the desired level of usability is

achieved. Prototyping was central to the rapid development, but the use of software

prototyping tools instead of paper-mock ups would reasonably have improved the

usefulness of the evaluations. The desired usability level was set to reach a specified fix

point, instead of attempting to achieve some absolute usability metrics as is typically

practiced. The former approach was apparently simpler to use without the broader

experience otherwise needed to write reasonable requirements.

Usability Engineering

This section will elaborate on the methodology used for the user interface design process, particularly focusing on Usability Engineering.

Introduction

Human-computer interaction (HCI) is a study of interaction between humans and

computers. It is an interdisciplinary subject, combining computer science with

other areas of study and research.

Design methods within HCI usually involve the concept of usability. The International

Standards Organization defines usability in the following way:

[Usability is the] extent to which a product can be used by specified users to

achieve specified goals with effectiveness, efficiency and satisfaction.

Achieving specified goals in a specified context of use, means that goals are set in advance, as well as the context of use. Effectiveness, efficiency and satisfaction are what

we need to measure to see if the goals have been met. Notably, usability is not a typical property of the system as most attributes are described in a requirements specification, but rather a quality of the interaction between the user and the system. The extent to which users participate in the development is determined by the choice of design process method.

On the other end, Participatory Design calls for full user involvement, and thus requires training and active cooperation. It can bring accurate information about users’ tasks and needs.

Usability Engineering focuses not on user participation or on maximizing usability, but on reaching a specified level of usability. Here, users may be involved in requirements elicitation and usability testing. The recommended activities for Usability Engineering are

1. User profiling

2. Task analysis

3. Defining usability goals through metrics and setting desired levels of usability to be

achieved

4. Analyzing the impact of possible design solutions (redesign)

5. Incorporating user-derived feedback in product design (prototype)

6. Evaluating the design by usability testing and iterating the development until the

planned usability levels are achieved