Rich domain modelling: a library story

Most software doesn't have a domain model. It has a database schema, a set of service classes that orchestrate calls to it, and a collection of user stories that have been implemented one by one, each leaving a small deposit of logic somewhere convenient. This works, until it doesn't — until a framework needs replacing, a regulation changes, or someone asks a question the system was never quite designed to answer, and the answer turns out to be scattered across fourteen service methods and three