If a use case diagram is modified due to a design omission, which diagrams would need to be revisited and potentially revised? During the design of interaction diagrams, if a missing actor is identified, which diagrams would need to be revisited and potentially revised? How important is it to keep the analysis models updated when changes are made to design models? This is an interesting question particularly in the context of Agile development. If analysis models are used to document business requirements decisions, how important is it to keep them current, especially prior to user acceptance testing?