MS Office back in the day was well known for being horrible to interoperate with. Their file format was literally a memory dump. So disconnecting enough that t

MS Office back in the day was well known for being horrible to interoperate with. Their file format was literally a memory dump. So disconnecting enough that the data on disk is at least serialized in to something that can be understood by others is good. Being disconnected enough so that V2, can load V1's persistence without too much pain is good. Again looking at you office. Persistence and domain models are fraternal twins, not identical twins. In general recognize that domain model, and persistence model are different things that have slightly different needs. For example the domain model of a person might only care about age, the persistence model is only going to care about DOB. So yeah 95% of the time they are the same and nothing is gained from separating them but having them be too close is often the source of problems.