Week 8 / Sixth Lecture : Identifying Needs and Establishing Requirements. [WeiTing]

• A requirement is a statement about an intended product that specifies what it should do or how it should perform. One of the aims of the requirements activity is to make the requirements as specific, unambiguous, and clear as possible.

• Requirements come in many different forms and at many different levels of abstraction, but we need to make sure that the requirements are as clear as possible and that we understand how to tell when they have been fulfilled.

Why establish requirements?

The activity of understanding what a product should do has been given various labels－for example, requirements gathering, requirements capture, requirements elicitation, requirements analysis, and requirements engineering.

• Requirement gathering and requirement capture imply that requirements exist out there and we simply need to pick them up or catch them.

• "Elicitation" implies that "others" (clients/ users) know the requirements and we have to get them to tell us.

• Requirements, however, are not that easy to identify.

• The term "requirements analysis" is normally used to describe the activity of investigating and analyzing an initial set of requirements that have been gathered, elicited, or captured. 

• Requirements engineering recognizes that developing a set of requirements is an iterative process of evolution and negotiation, and one that needs to be carefully managed and controlled. It is a better term than the others.

Different kinds of requirements :

• Functional requirements, which say what the system should do

• Non-functional requirements, which say what constraints there are on the system and its development. 

• Functional requirements capture what the product should do. 

• Data requirements capture the type, volatility, size / amount, persistence, accuracy, and value of the amounts of the required data.

• Environmental requirements or context of use refer to the circumstances in which the interactive product will be expected to operate. Four aspects of the environment must be considered when establishing requirements : 

1. Physical environment such as how much lighting, noise, and dust is expected in the operational environment. 
2. Social environment. The issues raised regarding the social aspects of interaction design, such as collaboration and coordination, need to be explored in the context of the current development.
3. Organizational environment, e.g., how good is user support likely to be and how easily can it be obtained.
4. Technical environment will need to be established: for example, what technologies will the product run on.

• User requirements capture the characteristics of the intended user group. 

• Usability requirements capture the usability goals and associated measures for a particular product. 

Data gathering

Data gathering is an important part of the requirements activity and also of evaluation.The purpose of data gathering is to collect sufficient, relevant, and appropriate data so that a set of stable requirements can be produced. It does help in determining requirements.

Data-gathering techniques :

1. Questionnaires
2. Interviews
3. Naturalistic observation
4. Studying Documentation

Reference : Preece, J., Rogers, Y., & Sharp, H. (2002). Interaction Design: Beyond Human-Computer Interaction. United State of America: Wiley Publisher.