Loading spreadsheet data into google maps

I am using spreadsheet data stored in google docs to generate a map of
base station sites. The basic code is taken from:

http://gmaps-samples.googlecode.com/svn/trunk/spreadsheetsmapwizard/makecustommap.htm

Additionally I have used polygon object to create the coverage area of
the network. However, now that I am done with the basic tasks I want
fully understand the original code. How it works. How does atom
publishing, json and google maps API interact. I would really like to
see an architectural map to understand this. Any help with drawing the
architecture of the API and its interactions would be appreciated.