The system should be easy to use.
The system should be flexible and scalable.
The system should be secured.
The system should be portable.
Did you read any requirements document and found one of the requirements statement mentioned above? Then, you started to think, what does it mean to make the software ease of use, how can I make that feasible, if I implemented that feature would the software became more usable? would it be acceptable from the customer? What are the metrics and acceptance criteria for that? How to transform these intangible requirements to something tangible can be implemented and measured.