We have analyzed two methods of diagnosis. A scoring system and an evaluation based on the validation of a criteria list. We have left the classic method which codes presence by a positive value and absence by a negative value and we have separated this concept from the representation of the value. Finally, the pattern Strategy defines a class of reasoning method. With the four patterns, we have defined four strategic points of the diagnostic system architecture which are not given by the semantical analysis of the domain.
Patterns give an assistance to refine existing objects and to discover new ones.
Diagnostic systems are relevant to Artificial Intelligence domain and AI community has often ignored software engineering problems. In medicine, the problems of maintenance are more acute. Medicine is in evolution so it needs to evolutive applications. Clinicians want interactive programs therefore systems must be efficient. Object-oriented methods and patterns are a good opportunity to progress in this way.