title: Domain model entities vs data entities, one or both in software architecture
body: <pre><code>**Update 2**
  </code></pre>
  
  <p>I have a project with a typical 3 layer structure(UI/Domain/Data layer). What is the pros and cons to have both domain model entities in domain layer and data entities layer.</p>
  
  <p>The possibility of changing to different database is slim. What is the pros and cons of having  only data entities in data layer as domain model entities? What is the difference if ORM is used (Is it good practice to have both entities when ORM (NHibernate) is used)?</p>
  
  <p>Please fire your ideas, or links, articles, books.</p>
  
  <p><strong>Update 3</strong></p>
  
  <p>In what circumstances we should use both domain entity and data entity?</p>