Architecture Patterns with Python

we should think in terms of verbs, not nouns. Our domain model is about modeling a business process. It’s not a static data model about a thing; it’s a model of a verb. So instead of thinking about a system for orders and a system for batches, we think about a system for ordering and a system for allocating, and so on. When we separate things this way, it’s a little easier to see which system should be responsible for what. When thinking about ordering, really we want to make sure that when we place an order, the order is placed. Everything else can happen later, so long as it happens.