UML - class model question

I have started to study UML standard and would need little help with two things I cannot find. I understand that in the class model I should design classes and their relations like:

Customer<>--->(*1)Items ordered

1)Is it correct that we design only "our" custom classes and do not care about classes used inside like Dictionary,List....?

2)What kind of relation is between server and clients (if each client is a class)? It is simple associative relation ServerClass---->*Client 开发者_如何学JAVAclass or agregation because client classes are created and maintained by server class? I guess its agregation but then I cannot think of any associative relation since there is always some master class.

Thank you!

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1) Typically, framework classes are not drawn. For list you just add the multiplicity > 1 (e.g. 1..*) to indicate that there are multiple items. UML is a language, i.e. a communication tool, thus, if the reader understands what you mean, you use the language well, if not, you may be more specific.

2) Be careful not to mix up objects and classes. Your if you have indeed multiple client classes, you can model all of them, if you on the other hand, have multiple client instances managed by the server, then in a class diagram you just make a one to many relationship from server to client.