[rules-users] Help with event not found over window query

[daveor]

Thanks for your email below. I needed to refactor my code somewhat to get this technique to work but it solved the problem that I had. 

I was previously using fireAllRules() but I refactored the code to use fireUntilHalt() instead, which required some additional work to make a couple of other supporting features behave properly. I know you don't strictly need to do this, but it needed to be done anyway and it made sense to do it now.

I would have thought it was quite a common scenario where someone wanted to implement business logic such as:

- Something happens
- It is expected that something else will happen within a certain time period of the first thing happening
- If the second thing doesn't happen within the time period, generate an alert

I ran into trouble because my various rules (from my original email) wouldn't fire an alert as expected when I fed in simulated events. 

I'm curious as to why you think it's interesting that the four rules below fail to meet my expectation? I suppose it's the fact that I'm a drools newbie and the issue here is probably just my inexperience mapping business logic into drools rules. 

daveor

On 15 Feb 2014, at 09:49, laune [via Drools] wrote:

> It would be interesting to discuss why each of these four rules fails to 
> meet you expectation. Mostly it's due to the engine not evaluating 
> exactly one minute after the "certain event" arrives. 
> 
> The following rule fires 1 minute after the evaluation of the arrival 
> of an Event according to constraints and when no second Event 
> (according to constraints not shown) has arrived since then. 
> 
> rule "Something Else" dialect "mvel" 
>     timer ( int: 1m ) 
> when 
>     $e1: Event($location: properties["location"] && ...) 
>     not Event(..., this after $e1) 
> then 
>    ... 
> end 
> 
> -W 
> 
> On 14/02/2014, daveor <[hidden email]> wrote:
> 
> > Hi there, 
> > 
> > I'm a drools newbie and I wonder if someone could help me. I'm using drools 
> > 6.0.1 and I'm trying to write a rule that fires when: 
> > 
> > 1) a certain event is seen and 
> > 2) a second event is not seen within a certain period of time (1 minute in 
> > the examples below) after the first event is seen 
> > 
> > I have tried the following LHS patterns: 
> > 
> > rule "Something" dialect "mvel" 
> > when 
> >     $e1: Event($location: properties["location"] && ...) 
> >     not Event(...., this after $e1) 
> > then 
> >     //do stuff 
> > end 
> > 
> > rule "Something" dialect "mvel" 
> > when 
> >     $e1: Event($location: properties["location"] && ...) 
> >     not Event(...., this after[0, 1m] $e1) 
> > then 
> >     //do stuff 
> > end 
> > 
> > rule "Something" dialect "mvel" 
> > when 
> >     $e1: Event($location: properties["location"] && ...) 
> >     List (size == 0) from collect (Event(..., this after $e1) over 
> > window:time(1m)) 
> > then 
> >     //do stuff 
> > end 
> > 
> > 
> > rule "Something" dialect "mvel" 
> > when 
> >     $e1: Event($location: properties["location"] && ...) 
> >     List (size == 0) from collect (Event(...) over window:time(1m)) 
> > then 
> >     //do stuff 
> > end 
> > 
> > The unwanted behaviours are as follows: 
> > 
> > In the first case, the rule fires immediately after the first event is 
> > inserted. 
> > In the second case, the rule fails to fire if the second event is seen (as 
> > expected) but the rule does not fire if the second event is not seen within 
> > 1 minute. 
> > In the third and fourth cases, the rule fires immediately after the first 
> > event is inserted. 
> > 
> > Event is a java class with a hash map of properties, defined with the 
> > following metadata: 
> > 
> > declare Event 
> > @role(event) 
> > end 
> > 
> > I would really appreciate if someone could help me out here. 
> > 
> > Thanks and let me know if you need any more info. 
> > 
> > Dave 
> > 
> > 
> > 
> > 
> > -- 
> > View this message in context: 
> > http://drools.46999.n3.nabble.com/Help-with-event-not-found-over-window-query-tp4028129.html
> > Sent from the Drools: User forum mailing list archive at Nabble.com. 
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