Suppose a hypothetical call chain:

 $printer->print() calls
  $document->print() calls
   $page->getContents() calls
    ...
     $image->getWidth()

One day you are given a small change request: documents will now be printed on yellow OR white pages. Thus images need to calibrate their colors. The color of the page is only known to the Printer, and only while it is running print(). But the Image has no access to the page color. Or the printer.

One solution is to add the page color as a parameter to each of the methods in the call chain. But this infects the methods with smelly EEK:
Extraneous Embedded Knowledge. They know more of the world than they should.

The talk will present some examples of design difficulties, like EEK, and how AOP solutions can help clean up the design.