title: Categories of design patterns
body: <p>The classic "Design Patterns: Elements of Reusable Object-Oriented Software" actually introduced most of us to the idea of design patterns.</p>
  
  <p>However these days I find a book such as "Patterns of Enterprise Application Architecture" (POEA) by Martin Fowler, much more useful in my day to day work.  </p>
  
  <p>In discussions with fellow developers, many make the (fair) point that frameworks like .NET are slowly starting to provide many of the patterns in the GOF book, and so why re-invent the wheel?</p>
  
  <p>It seems many developers think that the GOF book is the only reference worth having on design patterns.  So their logic goes that because frameworks (.NET etc) are providing many GOF patterns for us, patterns have seen their day and are no longer as important.</p>
  
  <p>Surprisingly (to me at least) when I mention the patterns descibed in POEA, I am often met with blank stares.  </p>
  
  <p>POEA proves that patterns are more than just Interators, Singletons, Commands etc.  I would also say that the patterns in GOF are really just a distinct "category" of patterns, applicable to a different (non-overlapping) level of design, than those in POEA.  </p>
  
  <p>So, what other "categories" of patterns have applied in your development?  What level of design do these patterns apply to?  At what point in the development process are they normally used?  Is there a book or reference for these patterns?</p>