Products are easier to reason about when you think of them as functions. They transform an input situation into an output situation.

This lets you describe what the product does as a transformation of the user’s circumstance instead of a bundle of features.

I’ve been using this thinking on a new project we’re working on at Postmark. I like this approach because it gives us a framework to communicate why something is a good idea to work on, and it focuses on the benefit for customers. If our answer to the question “How much better is this new outcome?” is “Not better enough”, then we need to define a better Output situation, which would lead to a better Process.