title: Associations' traversal direction
body: <p>I'm reading the book on <strong>Domain Driven Design</strong> of <strong>Eric Evans</strong> - <strong>Chapter 5</strong>, concerning <strong>associations</strong>. One of his advices to reduce complexity of a model is to impose a traversal direction for the associations. </p>
  
  <p>I quote:</p>
  
  <blockquote>
    <p>It is important to constrain relationships as much as possible. A
    bidirectional association means that both objects can be understood
    only together. When application requirements do not call for traversal
    in both directions, adding a traversal direction reduces
    interdependence and simplifies the design. Understanding the domain
    may reveal a natural directional bias.</p>
  </blockquote>
  
  <p>How to chose a traversal direction for an association? Generally, when there is an association between two elements, it may be read and understood in the two directions. What may cause us to chose one direction over the other?</p>
  
  <p>Thanks</p>