Time and again I see requirements mixed with specifications. The rule of thumb taught to designers is that requirements shouldn’t specify or suggest the solution. 

Why does this matter? It matters for two reasons

1. Requirements represent user needs, not the execution of the solution.
2. Requirements should inspire possibility

Designer Nathanael Boehm puts it simply here:

… it should be clear that the requirements are defined and accepted first and that they are fixed whereas the solution specified is just one way that the requirements can be met.