![enter image description here][1] [1]: http://i.stack.imgur.com/d4xNW.jpg Events, jobs, self and contact are nothing but DTO objects where each objects can be added, edited and deleted from database. I am not so familiar with use case diagrams so I wanted to know if this is correct or can be improved. Is there something to be generalised here? add edit and delete methods in implementations are handled by one class. but the call are handled separately for each object. Is this ok?