In some cases, the models may be very similar to one another. In other cases, the models may radically diverge. If your domain model and your data model are very similar, you can consider aggregating an instance of your data model class into your domain model class. If your domain and data models have a matching hierarchy and compatible interfaces, you can also consider using inheritance to derive your domain model classes from your data model classes.
摘自：
http://msdn.microsoft.com/en-us/library/hh404093