title: EF4.1: Possible to have zero-or-one to zero-or-one (0..1 to 0..1) relationship?
body: <p>.NET 4.0 with SQL Server 2008 R2.  I am trying to represent a 0..1 to 0..1 relationship and I keep getting the following error:</p>
  
  <blockquote>
    <p>Error 113: Multiplicity conflicts with the referential constraint in Role '{0}' in relationship '{1}'. Because all of the properties in Dependent Role are non-nullable, multiplicity of the Principal Role must be '1'.</p>
  </blockquote>
  
  <p>I get this message even when the properties in the dependent entity <em>are</em> nullable.  Is it possible to represent this relationship in Entity Framework?</p>
  
  <p>An example of when this might occur (independently of whether it is good database design to do so) is when you have a request that exists by itself, a result that becomes associated with it once the request is completed, and when the request is eventually pruned but the results all remain.</p>