i don't know whether it matter or not but i have seen there are 2 versions of servlet 3.0 specifications available. one is entitled SERVLET 3.0 December 2009 and the other is entitled SERVLET 3.0 REV a December 2010
i think i have got the solution. the specifications entittled Servlet 3.0 Rev a, is the maintainance release. read about the JCP process and various releases. this maintainence release comes after the final release. further the maintainence release incorporates clarifications where interpretations can conflict.