Often people have an idea but are not fully aware of what they really want. Certain usecases imply a biotope, where some user experience is possible. You may have a lot of products, therefore you need a category system, a searchengine, a database and all of those mandatory parts which make people experience and injoy life, with the designed lifestyle. Still many usecases are not simple enough or not smart enough and this is due to the lack of understanding the true nature of what shall be done respectively how it should be done. So you need a concept, a terminology, key visuals, semantics in interaction etc. Details matter and can make a huge difference. Is a category a tag, or is it an attribute, or a class? how is it be communicated? a lot of understanding is necessary to make things right from the beginning, even before anything has been done.It is a meta communication, to evaluate what should be done.