how easy do you think the concept of ternary association is to grasp for your readers, whent tehre is a higher multiplicity on one end?Īnd this leads to the question of what your system really do with emails.is Receiver really part of your system? If no, why is there a read() opeartion? If yes, what's the benefit of having a single system email system ?.If the answer is yes, you elminiate the association class. can an Email exist without a Sender or a Receiver? I often start to write an email and add the receivers later on (to avoid sending it by accident).who send() the Email: is it the Sender or is it the Email or is it the mailbox? It's not clear in your model where this responsibility lies.The question is how you want to see all these elements, i.e. Not to speak of the case were you would have Sender and Receivers beign composed with or inheriting from a common denominator EmailAccount.A ternary association as you have modelled it,.A Sender and a Receiver class, with Email being an association class.Email class with a composition with Reveiver and Sender if you'd see each sender or receiver as an embedded value object within the emails (so two emails with the same sender address would each have its own copy of the object).
Email class with an aggregation with Reveiver and Sender if you see those as a part of an Email which can be shared (between several emails referring to the same senders or receivers).Email class with associations with Receiver and Sender.There are plenty of ways to model the relationship between an email, a sender, and multiple receivers.
But think of it twice, because many people have difficulties reading ternary associations with hight multiplicity on one branch only. The main classes of the Car Service Center Management System are Car, Booking, Repair Car, Insurance, Customer, Payment.Yes, a ternary association is a possibility. Car Service Center Management System Class Diagram describes the structure of a Car Service Center Management System classes, their attributes, operations (or methods), and the relationships among objects.
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