(DEPRECATED) Apache Flink User Mailing List archive.

CEP API: Question on FollowedBy

classic Classic list List threaded Threaded
♦
♦
 4 messages Options
Anwar Rizal
Reply | Threaded
Open this post in threaded view
♦
♦
|

CEP API: Question on FollowedBy

Anwar Rizal
Hi All,


I saw Till's blog preparation. It will be a very helpful blog. I hope that some other blogs that explain how it works will come soon :-)

I have a question on followedBy pattern matching semantic. 


<citaton>

Non-strict contiguity means that other events are allowed to occur in-between two matching events. A non-strict contiguity pattern state can be created via the followedBy method.

Pattern<Event, ?> nonStrictNext = start.followedBy("middle");

</citation>

I try to use Till's examples in the blog, to understand the semantic of followedBy

--
First question.
Say, I have sequence of temperatures in a time window that corresponds to the within clause (say in 20 minutes).
 
TemperatureEvent(40) , OtherEvent(...), TemperatureEvent(30), TemperatureEvent(50), OtherEvent(...), TemperatureEvent(70), TemperatureEvent(65), TemperatureEvent(60)

say I want to match two TemperatureEvents whose temperatures > 35. 

What will be the matches in this case ?

  •  Will TemperatureEvent(40) , TemperatureEvent(50), match ? (because we have TemperatureEvent(30) at time 3 that does not match. 
  • Will TemperatureEvent(40) , TemperatureEvent(70) match ? (because the pair matches also the specification of pattern , the difference is we have TemperatureEvent(50) which happened before TempertureEvent(70) ). Similar question for TemperatureEvent(40) - TemperatureEvent(65) and TemperatureEvent(50)-TemperatureEvent(65) etc. pairs.


--
Second question.
For next (and also for followedBy) , I have also questions regarding example above:
Will TemperatureEvent(70), TemperatureEvent(65) and TemperatureEvent(65), TemperatureEvent(60) be returned , or the second pair is no longer returned because TemperatureEvent(65) has been used in the first pair ?



Is there a way to define the different sequence semantics  for the two questions I asked above ? 


Thanks,
Anwar.



 


 
Till Rohrmann
Reply | Threaded
Open this post in threaded view
♦
♦
|

Re: CEP API: Question on FollowedBy

Till Rohrmann

Hi Anwar,

yes, once we have published the introductory blog post about the CEP library, we will also publish a more in-depth description of the approach we have implemented. To spoil it a little bit: We have mainly followed the paper “Efficient Pattern Matching over Event Streams” for the implementation.

Concerning your questions:

1.) followedBy means that there can be an arbitrary sequence of events between two matching events, as long as they occur in the specified time interval. Thus, TemperatureEvent(40) will match together with TemperaturEvent(50), TemperaturEvent(70), TemperaturEvent(65) and TemperaturEvent(60).

2.) The same applies here for the next operator. It says that the second matching event has to follow directly after the previous matched event. However, a matching event can be part of multiple matching sequences. Thus, you will get TemperaturEvent(70), TemperaturEvent(65) and TemperaturEvent(65), TemperaturEvent(60) as two distinct matching sequences.

To make a long story short, there is currently no option to change the sequence semantics so that events are only part of one matching sequence. At the moment, events can participate in multiple matching sequences. I hope that answers your question Anwar.

Cheers,
Till

​

On Mon, Apr 4, 2016 at 11:18 AM, Anwar Rizal <[hidden email]> wrote:
Hi All,


I saw Till's blog preparation. It will be a very helpful blog. I hope that some other blogs that explain how it works will come soon :-)

I have a question on followedBy pattern matching semantic. 


<citaton>

Non-strict contiguity means that other events are allowed to occur in-between two matching events. A non-strict contiguity pattern state can be created via the followedBy method.

Pattern<Event, ?> nonStrictNext = start.followedBy("middle");

</citation>

I try to use Till's examples in the blog, to understand the semantic of followedBy

--
First question.
Say, I have sequence of temperatures in a time window that corresponds to the within clause (say in 20 minutes).
 
TemperatureEvent(40) , OtherEvent(...), TemperatureEvent(30), TemperatureEvent(50), OtherEvent(...), TemperatureEvent(70), TemperatureEvent(65), TemperatureEvent(60)

say I want to match two TemperatureEvents whose temperatures > 35. 

What will be the matches in this case ?

  •  Will TemperatureEvent(40) , TemperatureEvent(50), match ? (because we have TemperatureEvent(30) at time 3 that does not match. 
  • Will TemperatureEvent(40) , TemperatureEvent(70) match ? (because the pair matches also the specification of pattern , the difference is we have TemperatureEvent(50) which happened before TempertureEvent(70) ). Similar question for TemperatureEvent(40) - TemperatureEvent(65) and TemperatureEvent(50)-TemperatureEvent(65) etc. pairs.


--
Second question.
For next (and also for followedBy) , I have also questions regarding example above:
Will TemperatureEvent(70), TemperatureEvent(65) and TemperatureEvent(65), TemperatureEvent(60) be returned , or the second pair is no longer returned because TemperatureEvent(65) has been used in the first pair ?



Is there a way to define the different sequence semantics  for the two questions I asked above ? 


Thanks,
Anwar.



 


 
Anwar Rizal
Reply | Threaded
Open this post in threaded view
♦
♦
|

Re: CEP API: Question on FollowedBy

Anwar Rizal
Thanks Till. 

The only way I can change the behavior would be to post filter the result then. 

Anwar.

On Tue, Apr 5, 2016 at 11:41 AM, Till Rohrmann <[hidden email]> wrote:

Hi Anwar,

yes, once we have published the introductory blog post about the CEP library, we will also publish a more in-depth description of the approach we have implemented. To spoil it a little bit: We have mainly followed the paper “Efficient Pattern Matching over Event Streams” for the implementation.

Concerning your questions:

1.) followedBy means that there can be an arbitrary sequence of events between two matching events, as long as they occur in the specified time interval. Thus, TemperatureEvent(40) will match together with TemperaturEvent(50), TemperaturEvent(70), TemperaturEvent(65) and TemperaturEvent(60).

2.) The same applies here for the next operator. It says that the second matching event has to follow directly after the previous matched event. However, a matching event can be part of multiple matching sequences. Thus, you will get TemperaturEvent(70), TemperaturEvent(65) and TemperaturEvent(65), TemperaturEvent(60) as two distinct matching sequences.

To make a long story short, there is currently no option to change the sequence semantics so that events are only part of one matching sequence. At the moment, events can participate in multiple matching sequences. I hope that answers your question Anwar.

Cheers,
Till

​

On Mon, Apr 4, 2016 at 11:18 AM, Anwar Rizal <[hidden email]> wrote:
Hi All,


I saw Till's blog preparation. It will be a very helpful blog. I hope that some other blogs that explain how it works will come soon :-)

I have a question on followedBy pattern matching semantic. 


<citaton>

Non-strict contiguity means that other events are allowed to occur in-between two matching events. A non-strict contiguity pattern state can be created via the followedBy method.

Pattern<Event, ?> nonStrictNext = start.followedBy("middle");

</citation>

I try to use Till's examples in the blog, to understand the semantic of followedBy

--
First question.
Say, I have sequence of temperatures in a time window that corresponds to the within clause (say in 20 minutes).
 
TemperatureEvent(40) , OtherEvent(...), TemperatureEvent(30), TemperatureEvent(50), OtherEvent(...), TemperatureEvent(70), TemperatureEvent(65), TemperatureEvent(60)

say I want to match two TemperatureEvents whose temperatures > 35. 

What will be the matches in this case ?

  •  Will TemperatureEvent(40) , TemperatureEvent(50), match ? (because we have TemperatureEvent(30) at time 3 that does not match. 
  • Will TemperatureEvent(40) , TemperatureEvent(70) match ? (because the pair matches also the specification of pattern , the difference is we have TemperatureEvent(50) which happened before TempertureEvent(70) ). Similar question for TemperatureEvent(40) - TemperatureEvent(65) and TemperatureEvent(50)-TemperatureEvent(65) etc. pairs.


--
Second question.
For next (and also for followedBy) , I have also questions regarding example above:
Will TemperatureEvent(70), TemperatureEvent(65) and TemperatureEvent(65), TemperatureEvent(60) be returned , or the second pair is no longer returned because TemperatureEvent(65) has been used in the first pair ?



Is there a way to define the different sequence semantics  for the two questions I asked above ? 


Thanks,
Anwar.



 


 
Till Rohrmann
Reply | Threaded
Open this post in threaded view
♦
♦
|

Re: CEP API: Question on FollowedBy

Till Rohrmann
Yes exactly. This is a feature which we still have to add.

On Tue, Apr 5, 2016 at 1:07 PM, Anwar Rizal <[hidden email]> wrote:
Thanks Till. 

The only way I can change the behavior would be to post filter the result then. 

Anwar.

On Tue, Apr 5, 2016 at 11:41 AM, Till Rohrmann <[hidden email]> wrote:

Hi Anwar,

yes, once we have published the introductory blog post about the CEP library, we will also publish a more in-depth description of the approach we have implemented. To spoil it a little bit: We have mainly followed the paper “Efficient Pattern Matching over Event Streams” for the implementation.

Concerning your questions:

1.) followedBy means that there can be an arbitrary sequence of events between two matching events, as long as they occur in the specified time interval. Thus, TemperatureEvent(40) will match together with TemperaturEvent(50), TemperaturEvent(70), TemperaturEvent(65) and TemperaturEvent(60).

2.) The same applies here for the next operator. It says that the second matching event has to follow directly after the previous matched event. However, a matching event can be part of multiple matching sequences. Thus, you will get TemperaturEvent(70), TemperaturEvent(65) and TemperaturEvent(65), TemperaturEvent(60) as two distinct matching sequences.

To make a long story short, there is currently no option to change the sequence semantics so that events are only part of one matching sequence. At the moment, events can participate in multiple matching sequences. I hope that answers your question Anwar.

Cheers,
Till

​

On Mon, Apr 4, 2016 at 11:18 AM, Anwar Rizal <[hidden email]> wrote:
Hi All,


I saw Till's blog preparation. It will be a very helpful blog. I hope that some other blogs that explain how it works will come soon :-)

I have a question on followedBy pattern matching semantic. 


<citaton>

Non-strict contiguity means that other events are allowed to occur in-between two matching events. A non-strict contiguity pattern state can be created via the followedBy method.

Pattern<Event, ?> nonStrictNext = start.followedBy("middle");

</citation>

I try to use Till's examples in the blog, to understand the semantic of followedBy

--
First question.
Say, I have sequence of temperatures in a time window that corresponds to the within clause (say in 20 minutes).
 
TemperatureEvent(40) , OtherEvent(...), TemperatureEvent(30), TemperatureEvent(50), OtherEvent(...), TemperatureEvent(70), TemperatureEvent(65), TemperatureEvent(60)

say I want to match two TemperatureEvents whose temperatures > 35. 

What will be the matches in this case ?

  •  Will TemperatureEvent(40) , TemperatureEvent(50), match ? (because we have TemperatureEvent(30) at time 3 that does not match. 
  • Will TemperatureEvent(40) , TemperatureEvent(70) match ? (because the pair matches also the specification of pattern , the difference is we have TemperatureEvent(50) which happened before TempertureEvent(70) ). Similar question for TemperatureEvent(40) - TemperatureEvent(65) and TemperatureEvent(50)-TemperatureEvent(65) etc. pairs.


--
Second question.
For next (and also for followedBy) , I have also questions regarding example above:
Will TemperatureEvent(70), TemperatureEvent(65) and TemperatureEvent(65), TemperatureEvent(60) be returned , or the second pair is no longer returned because TemperatureEvent(65) has been used in the first pair ?



Is there a way to define the different sequence semantics  for the two questions I asked above ? 


Thanks,
Anwar.



 


 
Free forum by Nabble Edit this page