in Harmony ESW process you added User Stories as an additional starting point to the Microcycle. I think User Stories are usually used to describe the "problem" or "expectation" of a stakeholder regarding the "product". It is maybe something like a high level requirements elicitation approach, which differs from Use Cases.
What are your experiences and best practices to work with User Stories (e.g. high level approach) and Use Cases (e.g. detailed approach) regarding high-fidelity modelling and requirements refinement?
Do you have a taxonomy regarding requirements, use cases, user stories and modelling?
There is a great post here: http://blog.hood-group.com/blog/2013/05/15/use-case-und-user-stories-verbundete-oder-feinde/.
Unfortunately, it is in German language. However, in short: An user story is an instrument to plan tasks in an agile development process. An use case contains much more architectural information and is used to model high-level views of interactions between the system to develop and the users/actors. An user story can be viewed as an use case slice which means the part of the use case which can be developed in one cycle.
I just gave a workshop in India last week on this very topic. To my mind, a user story is equivalent to a scenario - a singular thread with perhaps minor variation. A use case contains several (typically 3-25) user stories. User stories have a canonical form "As a <role>, I want <feature> to achieve <goal>". As such, user stories are suitable for simple flows; more complex flows are better modelled as scenarios. Coherent collections of such flows constitute a use case. Both user stories and scenarios represent to a small number of requirements.
At the other end of the scale, use cases are sized to be implemented in a single iteration. Epics are like high level use cases that require multiple iterations for implementation. This is done by breaking the epic up into multiple use cases.
Does that help clarify it?