title: Optional participation in database design and crow's foot notation
body: <p>Given a relationship such that:</p>
  
  <p>TAXI -> has -> ROUTE -> driven by -> ASSIGNED_TRANSPORT</p>
  
  <p>Is the relationship from route to assigned_transport, zero, one or many (that is, a one-to-many connectivity with optional participation, <strong>OR</strong> would it be a one to many (that is, mandatory participation rather than optional participation)?</p>
  
  <p>That is, I don't understand optional participation, could you correctly argue that when a route is newly assigned by the taxi company, it will most likely have no assigned_transport assigned to it yet at a given point in time (of course later it most certainly will). Is this how you could correctly argue for optional participation?</p>
  
  <p>Basically I am confused as to how to judge whether there is an optional participation between two entities...</p>
  
  <p>I suppose on the contrary, you could also argue that, if there is an entity instance in the assigned_transport table, you would expect that an assigned_transport instance to be assigned to a particular route (otherwise, there would be no point in assigning transport if it has no route!)... hence assigned_transport would be mandatory, not optional?</p>
  
  <p>So I'm not sure which of it is logically correct...</p>
  
  <p>Am I on the correct track?</p>
  
  <p>Thank you for your assistance.</p>