1、 The function of requirement is not realized.
2、 Realized the function that the demand has no requirement.
3、 There are clearly specified mistakes that should not be made in the software.
（Extension: what are the two basic elements of software?
1） Function should be able to achieve
2） To have strong exception handling capability (robustness)
4、 Although demand is not mentioned explicitly, the function that should be realized has not been realized.
（Note: Requirements may have omissions, we can not test the work because the requirements have problems, resulting in testing problems.
5、 Software is difficult to understand, difficult to use, slow to run and so on stand in the user’s point of view all feel bad place.