Was the GDP of Berlin higher or lower in 2015 than it was in 2014?
return Berlin ;return GDP of #1 ;return #2 in  2015 ;return #2 in  2014 ;return if #3 is higher than #4 ;return if #3 is lower than #4 ;return which is true of #5 ,  #6
['select', 'project', 'filter', 'filter', 'boolean', 'boolean', 'comparison']