Customer participation is the only way to avoid the expected difference (Expectation GAP), which is not consistent between the products that customers expect and the products designed by developers. However, only simply asking one or two customers in the beginning of the project, then start coding, do not have enough. If the developer only develops software for customers to develop software, they may have to develop, because customers often don't know their truly needs, and developers don't know. The user proposes that the "need" is not always equivalent to the functionality required to use new products to handle their tasks (T A s K). Therefore, when you collect the opinions of the user, you must analyze and organize these demand opinions until you understand it, write your understanding as a document, and then discuss with users, this is a repetitive process, and take time . If you don't spend this aspect, you don't reach a consensus on the expected product - the final consequence may be rework, and the product is not satisfactory.
