Bottom-up design is an approach to information processing that involves piecing together components and systems to form grander, more inclusive overall schemes.  Bottom-up processing is how we are able to form a single perception of reality from multiple sources of sensory input.  Though this design is one typically involved in synthesis I prefer to apply it to my artistic research process.  My research involves specific and in-depth study of a multitude of seemingly unrelated concepts; really, they are just ideas and information I find interesting.  Once I have assimilated the information I can use it.  Through contemplation I find the unseen connections between the random pieces, and gradually, a larger structure emerges- or rather, my understanding makes me able to perceive the more complex system.     
 
The top-down method is an approach to information processing that involves the breaking down of a concept into its various smaller components thus creating one or more subsystems of the original system.  This is typically how we analyze or deconstruct information.  Lately I have been taking this approach with my artwork.  I start with the very vague concept of a piece and then approach it as though I was solving a math or science problem.  As I begin working, I begin to understand some of the underlying concepts and my idea becomes less vague.  As I continue analyzing my original concept, it becomes more specific and fine tuned. Subsequently, the piece also becomes refined. Subtle detail alludes to the subcomponents of the main components of the overall piece.