Have you fully explored what the problem-behind-the-problem is

Is the problem statement correctly formulated

Is the list of stakeholders complete and correct

Does everyone agree on the definition of the system boundaries

If system boundaries have been expressed using actors, have all actors been defined and correctly described

Have you sufficiently explored constraints to be put on the system

Have you covered all kinds of constraints - for example political, economic, and environmental

Have all key features of the system been identified and defined

Will the features solve the problems that are identified

Are the features consistent with constraints that are identified