title: IOC and interfaces
body: <p>I have a project structure like so :-</p>
  
  <pre><code>CentralRepository.BL
  CentralRepository.BO
  CentralRepository.DataAccess
  CentralRepository.Tests
  CentralRepository.Webservices
  </code></pre>
  
  <p>and there is an awful lot of dependencies between these.  I want to leverage unity to reduce the dependencies, so im going to create interfaces for my classes.  My question is in which project should the interfaces reside in.  My thoughts are they should be in the BO layer.  Can someone give me some guidance on this please</p>