Quality is an open concept. Something has a good quality when the most salient of its characteristics have a positive value. What are this relevant features? It depends on the interest of who is judging the quality. Therefore the idea of quality can be separated neither from the object under examination, nor from the point of view selected by the evaluator. It is important also to choose when and how to evaluate quality. This paper -realized within the PRIN -National Interest Research Project- entitled "Comunit