Problems with PBD or PBE:

How to infer the user's intent. The user's intent as expressed in examples is to be divined by the system and turned into a useful generality. Since human have a very large range of intents with extreme context restrictions, overlapping window interface serve to restrict context while giving the user the illusion of freedom. The process of inferring a user's intent in selecting a particular object has been described by Dan Halbert as 'data description'. For instance, the user are interpreting the interface in terms of their goals and sometimes they are imperceptibly in making decision. Another influence is complication in the flow of control. Since repetitive activities often include special cases, therefore, it mus be handled differently. For example, redo the activity or deciding which way to follow in order to get the tasks/actions in a minimal time and accurate.