Requirements, Not Solutions

Just as there is a difference between business requirements and technological requirements, so there is a difference between a requirement and its solution. It is important to your requirements discovery that you do not write solutions instead of requirements.

The requirements we are discussing here are business requirementsthat is, the things needed by the business within the work context regardless of the technology employed. In Chapter 5, we explored the essence of the business, including why it is necessary to understand the essence and not its implementation. We are saying exactly the same thing here: The business requirements are written to reflect the essence, and not any assumed implementation.

Why is this important? Because it is far too easy to hide important functionality by describing an implementation, and far too easy to select the most obvious implementation when better ones may exist. The following, which was taken from an online shopping system, is not a requirement; it's a solution:

The product shall display pictures of goods for the customer to click on.

The requirements analyst has assumed a screen, a picture, and ordering by clicking. Here's the correct way to write this requirement:

The product shall enable the customer to select the goods he wishes to order.

By writing a solution instead of the essential requirement, the analyst precludes the possibility of other implementations, such as ordering by mail, catalogue, mobile or land telephone, or sales representative's visit.