Client / Server Model

When designing a new application you usually have in mind a big picture of the future application and maybe you know a given system should be decomposed as the client / server models dictates.

But when in the analysis this factor comes important? In which part of the document should you split the server and client functionalities?

I am not really sure what would be the best approach to solve this problem, for sure it depends on what the client wants you to design but what if other client is not that sure?

For the first kind of client I came across with a simple solution, just include the client/server model as a design constraint and go on with the analysis.

If instead of the client it’s you who finds out that the client/server model is the best one which fits the system architecture I think you shouldn’t consider the client/server model till the design stage.