real time - How to make esper epl divide section and compare value -

i new using esper. don't know esper epl, i'm in trouble.

problem this.

user define value section.

for example,  level1 : 1~3 level2 : 4~6 level3 : 7~9 

so when data come first, check section , make events. previous value , new value same level nothing (ex. prev value=1, next value=2 these in same level1).

in other words, when data come, check previous value , level. if have different level, something.

esper epl can this? how can make it?

the "prior" , "prev" both give access event before given event. sql standard "case when then" if-then-else of sql standard. this:

insert categorizedstream select   case when value between 1 , 3 1     when value between 4 , 6 2    when value > 6 3  end level someevent;  select * categorizedstream(prior(level) != level); 

one use prior , case-when in 1 epl statement think becomes more readable using 2 statements.