Domain models in Enterprise Architect are created using Class diagrams, which define domain objects like Bill, BillItem, PriceList, and Book without attributes. Relations between domain objects, such as Bills containing BillItems and Bills being contained in Books, are modeled using aggregation links. Enterprise Architect includes transformation templates that allow domain models to be transformed to other models, like C# or DDL, by right clicking on a package and selecting the transformation and destination. Transformation templates automatically generate new classes with required properties.