In my deliverables it says 'Create either a Sequence of Collaboration' diagram for each use case provided. Well on the 'Use Case Diagram' (which the fictional BA provides) there are 3 use case bubbles for which there are no use cases described (e.g. 'Log in'). Do you think I still have to diagrams for these? Some of the other uses cases feed in and out of them.
Lastly, if the use case contains 'alternative flows' do these have to be described within the sequence/collaboration diagram?