CEP condition expression and its event consuming strategy

[Chao Wang]

Hi,

I have two questions regarding the use of the Flink CEP library 
(flink-cep_2.11:1.3.1), as follows:

1. I'd like to know how to use the API to express "emit event C in the 
presence of events A and B, with no restriction on the arriving order of 
A and B"? I've tried by creating two patterns, one for "A and then B" 
and the other for "B and then A", and consequently using two 
patternStreams to handle each case, which emits C. It worked but to me 
this approach seems redundant.

2. Given the above objective expression, how to consume the accepted 
events so that they will not be used for future matchings? For example, 
with the arriving sequence {A, B, A}, the CEP should only emit one C 
(due to the matching of {A,B}), not two Cs (due to {A,B} and {B,A}). 
Similarly, with the arriving sequence {B, A, B, A}, the CPE should only 
emit two Cs, not three.


Thanks,

Chao