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<pre>
+-----------------------+	+-------------------------------+
|	Observer	|---->*	|	     Subject		|
|-----------------------|	|-------------------------------|
|update()		|<--+	|registerObserver(&$observer)	|<-------+
|			|   |	|				| 	 |
|			|   |	|unregisterObserver(&$observer)	|<-------+
|			|   |	|				| 	 |
|			|   |	|notifyObservers()		|<-------+
|			|   |	|				|	 |
+-----------------------+   ^	+-------------------------------+	 |
			    |						 |
+-----------------------+   |						 |
|	RSS		|   |						 |
|-----------------------|   ^						 |	
|update()		|---+						 |
|			|						 |
|updateFeed()		|						 |
|			|						 |
|			|						 |
|			|						 |
+-----------------------+						 |
									 |
				+-------------------------------+	 ^
				|	     Article		|	 |
				|-------------------------------|        |
				|registerObserver(&$observer)	|<---+   |
				|				|    |	 |
				|unregisterObserver(&$observer)	|<---+---+
				|				|    |
				|notifyObservers()		|<---+
				|				|
				+-------------------------------+
</pre>