[rules-users] sliding window question

[Wolfgang Laun]

The correct way to ascertain that something hasn't happened for
a certain interval must be based on "staking out" this interval. One
way is by means of two distinct events:

   when
     $r1: Reading( reading >90 )
     $r2: Reading( reading > 90, this after[30s] $r1 )
     not Reading( reading <= 90, this after $r1 && before $r2 )
   then

Clearly, this will only work if  Readings arrive regularly, and you may have a
certain amount of delay at the end.

Another way would be to use a sliding window over time:

   when
     not Reading( reading <= 90 ) over window:time( 30s )
   then

Here's a snag, too: If there are no readings at all, you'll also get an alert.

And then you'll have to think about the seconds following the 30th
second: should another alert be emitted repeatedly...

Most of the time, it's not an issue in CEP ;-)

-W






On 27/02/2014, lin.lin <lin.lin at comcast.net> wrote:
> Hi,
>
> I tried to create a rule that gives an alert when a machine reading is high
> for 30 seconds. I modeled the machine reading input as events.  The
> following is the rule:
>
> rule "rule1"
> dialect "mvel"
>     when
>        $rd1 : mReading( reading >90 ) from entry-point ReadingStream
>        not ($rd2 : mReading (reading<=90 , this before [0s, 30s] $rd1 )
> from entry-point ReadingStream )
>     then
>       System.out.print ("alert: Reading high for 30 seconds \n");
> end
>
> This does not detect detect the bad reading.  However, If I changed the
> rule
> to be following (change second condition from "not" to "exists"), it
> detects
> all readings that are good.
>
> rule "rule1"
> dialect "mvel"
>     when
>        $rd1 : mReading( reading >90 ) from entry-point ReadingStream
>        exists ($rd2 : mReading (reading<=90 , this before [0s, 30s] $rd1 )
> from entry-point ReadingStream )
>     then
>       System.out.print ("alert: Reading high for 30 seconds \n");
> End
>
>
> Is this an issue in CEP or did I do something wrong?
>
> Thanks a lot!
> Lily
>
>
>
> --
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