Which is why I prefer working with a strongly typed functional language. Domain Driven Development (well, my version of it) is the first step. Get all the types

Which is why I prefer working with a strongly typed functional language. Domain Driven Development (well, my version of it) is the first step. Get all the types right. The necessary operations should be obvious by this point. Code them up! Write unit tests as you go along. You're likely to do some refactoring as your operations materialize, and unit tests are going to help you stay safe.