Andrew,

Thank you for your explanation. I am vaguely understand what you are 
talking about.

This "magic" rails is doing is most difficult part for me. I found few 
literacy explain rail "magic" well. I am reading "agile web development 
with rail" and rails online documents. They both mentioned that for 
example like

    respond_to do |format|
      format.html # index.html.erb
      format.xml  { render :xml => @posts }
    end

controller will respond to user either html or xml with the right format 
provided by request url. That's it. They don't explain why these two 
statements will not be executed sequentially or anything behind the 
scene. I have big difficult time to understand since I am coming from a 
c++, python world.

How can I accrue my knowledge on this "magic"? Any in depth 
books/documents I can refer to?

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