What order of diagram should i have to use

Question

hi there i took software engineering this term. our teacher said that when we want to analysis an application at the first step we should have to design the Use Case Diagram and then design the class diagram and finally design the sequence diagram but in bags book has different ways to design its says that fist of all design the use case then sequence and then class diagram. would you please to tell me what is the relation between them. i know we could find the class method by the sequence. but my main problem is that when i want to analysis my project i little bit mix up with sequence because some of the class does not exist but how can we make the object of the class that does not exist. the ways that our teacher said using the Boundery object and entity and control (should i have to add them to our class diagram ) how can we found that our design is correct or not.

Answer 1

This is more theoritical, I can tell you this :

There is a sequence to it, but our mind works parallely so,

1) Use case : The use case diagram identifies a proper case, it shows the steps to fulfill your requirement/needs. Proper steps

2) Sequence Diagram : In order to satisfy your requirements, there should be flow of data/action/information and dependency of the result (Output of one is input for another)

3) Class Diagram : When you start the sequence, you need the object, classes which actually interacts and passes the messages (methods) with data.

So, mainly sequence and class diagram sometimes go together, as when you think about sequence, you start forming the class, and when you form the class (state and behavior), you form the sequence of it to achieve the use case.

Hope this helps