Chapter 11: Discovering Requirements in Interaction Design

The crucial early phase of discovering requirements in interaction design involves exploring the problem space to define precisely what the new product will be, focusing on the target users, their tasks, goals, contexts, and various system constraints. While requirements activity is inherently iterative and closely linked with design and evaluation, successful completion requires clearly articulating requirements to prevent technical miscommunication. Requirements are broadly classified as functional requirements, which detail the product's intended actions, and nonfunctional requirements, which specify the constraints and characteristics of the system, such as performance or platform compatibility. Other vital requirement types include data requirements (covering data accuracy, volatility, and persistence), environmental requirements (context of use, encompassing physical, social, organizational, and technical factors), user characteristics (abilities and expertise, often compiled into a user profile), and essential usability and user experience goals. Requirements can be explicitly captured using structured formats like the Volere atomic requirements shell or, especially in agile development, through user stories, which represent small units of customer value written in the simple structure of: "As a (role), I want (behavior) so that (benefit)". Large stories, known as epics, must be broken down before implementation. Data gathering for requirements utilizes traditional methods (observation, interviews) alongside reviewing documentation and researching existing products. Specialized techniques include Contextual Inquiry, a highly structured field research process that uses one-on-one contextual interviews based on a master/apprentice relationship to observe and interpret user activities. Contextual Inquiry is guided by principles like context, partnership, interpretation, and focus, and seeks to identify needs based on concepts of joy of life and joy of use. Additionally, probes—such as cultural, design, technology, and provocative probes—are used to imaginatively engage users and gather rich contextual data. To make requirements tangible, designers create personas, which are realistic syntheses of typical users centered around specific goals, and scenarios, which are informal narrative descriptions of user activities that explore current or future product use. Finally, use cases capture interaction details in a step-by-step manner, with essential use cases focusing on dividing tasks between the user and the system, while detailed use cases specify the normal course of interaction and potential alternative courses. Brainstorming also serves as a crucial technique for generating innovative ideas and requirements.