For many products, the spec is determined by what a customer will buy. And until a customer actually buys the product, the spec is just a well informed guess.

During product development, the spec is an iterative process. Engineering or marketing starts by saying "This is a good product." But there is always a lot of intellectual incest within a company. Everyone spends their time talking with each other. The makers of a product frequently do not use the product, and so no one really knows what is needed in a new product.

So, sales takes the specs to customers, who say it is not so good, but would be great if it came with a blue LED.

Engineers dismiss this as feature creep, and complain about having to modify their perfect design. But this process can also be known as listening to your customers.

Erik is wise to create his designs with enough flexibility to handle this process.