> When concurrent changes happen, the database simply stored each conflicting value. Yes, this is the key! 1. store everything, 2. give the domain modelers an

> When concurrent changes happen, the database simply stored each conflicting value. Yes, this is the key! 1. store everything, 2. give the domain modelers an array of strategies to merge particular cases, with the default being conflict-and-bother-the-user. Every existing merge strategy can be represented on top of this model, so it should be the base layer. The conflict resolution strategies can be sliced up, layered, hidden, or exposed to the user according to the design criteria because conflict resolution is part the problem domain. I would go so far as to say that assuming one particular merge strategy for all data structures as 'correct' is actively harmful. What is the worst case outcome in the example above? That nobody looks at it. In a general case like this choosing any default action at all is the wrong call because both edits were made with different assumptions and contexts, and that's the level where the conflict should be resolved, not down here in the invoice.