title: Cross cutting concern example
body: <p>What is a good example of a <code>cross-cutting concern</code>? The medical record example on the <a href="http://en.wikipedia.org/wiki/Cross-cutting_concern">wikipedia</a> page seems incomplete to me. </p>
  
  <p>Specifically from this example, why would logging lead to code duplication (<em>scattering</em>)? (Besides simple calls such as <code>log("....")</code> everywhere, which doesn't seem like a big deal). </p>
  
  <p>What is the difference between a <code>core concern</code> and a <code>cross-cutting concern</code>?</p>
  
  <p>My end goal is to get a better understanding of AOP. </p>