To me domain model is an Object-Oriented API through which I can interact with the data in the system. Another way to interact would be direct SQL-calls of cou

To me domain model is an Object-Oriented API through which I can interact with the data in the system. Another way to interact would be direct SQL-calls of course, but then users would need to know about how the data is represented in the database-schema. Whereas with an OOP API, API-methods return instances of several multiple model-classes. The way the different classes are associated with each other by method calls makes evidednt a kind of "theory" of our system, what kind of objects there are in the system what operations they can perform returning other types of objects as results and so on. So it looks much like a "theory" might in Ecological Biology, m ultiple species interacting with each other.