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