Should all classes appear in sequence diagram?

[Paul Chen]

I have 20-25 classes in class diagram.Should all classes appear in sequence diagram? If so, sequence diagram will be much repeated,longer and wider. If not, how to obey consistence of system architecture.
Hope someone give me suggestion.
Thx

[Iyn Shri]

Hi paul...
Can u pls tell me what's yr approach ? According to what I know u just need to identify the classes... then design the seq diag using those objects and then design the class diag from the seq diag... I think class diag will be more detailed than the seq diag in the sense u may have more classes in the class diag...
Correct me if I am wrong...
Cheers..
Vidya

[Alberto Dell'Era]

My opinion is that only classes that are strictly involved in the flows of messages are to be included in the diagram; sometimes you can leave out some of them (perhaps you call a method getCurrentUser() on an instance of a class, and you don't show in the diagram that the method is calling, say, two Entity beans to fullfill the request, but you show just that method returning the user).
This is the eternal fight between precision (show every detail) and concision (show only what's relevant). Your goal should be to communicate an idea: if your sequence diagram is showing how the system get the shopping cart of the user, you may stick to that, and assume that the reader (watcher?) of the diagram it's not interested in how you get the current user.
[Perhaps there will be another diagram that shows exacly that, named "Get Current User" ...]
Unnecessary details just clutter the diagram, and confuse the reader.
In my very humble opinion, it's much, much more difficult to produce a concise design than a "verbose" one. It takes dedication and careful thinking, but it really pays afterwards. I think that the Great Evaluators of the SCEA Part II know that quite well, and appreciate; I hope that I'm not just dreaming ...
Alberto

[herve attia]

Well, make your sequence diagram simple !
Show only the main objects. Avoid to display Home/Remote. Wrap them into Business delegate.
Also, as sequence diagram is only 20 points. Do not spent too much time on it.
I made them SIMPLISTIC, READABLE and CONSISTENCY !
herve
scjp, scdj, scwd, scea

[Paul Chen]

Thanks for comments.
When design, which should be earlier order between Sequence diagram and class diagram? This is also to ask a question, which is more abstract between them?
In most books, sequence diagram is in the later chapter than class diagram. So it seems sequence diagram should be more detailed.
please correct me and thanks,
Paul

[Iyn Shri]

Hi...
Should we show the required patterns such as presentation tiers, Bussinees & Integrations (Front Controller, View Helper, Bussiness delegate, service Locator, Session facade, DAo, VO) in the seq diag.. or should we should we show these patterns only in the class diag... How is it ?? I am just planning to include the patterns session facade, DAO, VO (wherever needed) in the seq diag but make the class diag more elaborate by using the other patterns... Am I right ??? It is true that we need not spend much time in the seq diag.. but since I don't know how detailed it should most of my time is spent on it.. still I am not thru with it... Would really appreciate if anyone can throw some light on this... will help me to move forward....
Thanks,
Vidya