'When we set out to write software, we never know enough. Knowledge on the project is fragmented, scattered among many people and documents, and it's mixed with other information so that we don't  even know which bits of knowledge we really need. Domains that seems less technically daunting can be deceiving: we don't realize how much we don't know. This ignorance leads us to make false assumptions.'

(Eric Evants - 'Domain-Driven Design - Tackling Complexity in the Heart of Software')