tag:blogger.com,1999:blog-7831813422886730737.post1087333542599346836..comments2023-10-08T10:44:28.524+03:00Comments on Event Processing Thinking: The semantic overload of derived events Opher Etzionhttp://www.blogger.com/profile/10791357917675270335noreply@blogger.comBlogger4125tag:blogger.com,1999:blog-7831813422886730737.post-16444422597489434132012-09-30T18:51:47.971+02:002012-09-30T18:51:47.971+02:00Couldn't one make the case in the toll road ex...Couldn't one make the case in the toll road example that there are two events on exiting the toll road? <br /><br />One is the sensor stating "Car arrived at Booth exiting" which has minimal information car, time, booth, etc. <br /><br />However, there is a second event that indicates that the toll trip has completed. "Trip Completed" which has a richer set of information car, time entering, time exiting, booth entered, booth exited, mileage, ave speed, fare.<br /><br />There are two nouns in a sense: the car and the trip. The trip is definitely derived (and bounded) by the car's two events of entering and exiting. There is a specific purpose for the car being at those two points in space-time. So, there is a relationship between these two points which is called a trip that is implicit. We can't directly sense a trip, but we do know that when a car enters and subsequently exits the toll road, that a trip has occurred. To me, it seems that this fits your first type of derive. And I can have a more rich set of information on a derived event that on the events used in the deriving showing that the whole is greater than the sum of the parts.<br /><br />In addition, we could enrich this trip noun even further if we had sensors that could identify a car (such as by license plate) as it entered then we could observe such things as entering and leaving rest areas or travel plazas derving the time spent at the stops which in turn would improve the average speed calculation.<br /><br />The could also have a higher level of noun called the traveller that contained a collection of trips. To see how much reuse the toll road was given or if it made sense to implement a frequent traveller program or where to invest in plazas.<br /><br />My point is that the noun (the thing that changes state) is in the eye of the beholder and there are implicit relationships that once found, can be a game-changer.J Writer Dudehttps://www.blogger.com/profile/06274249105607263907noreply@blogger.comtag:blogger.com,1999:blog-7831813422886730737.post-4643876732462858462012-09-26T11:34:33.556+02:002012-09-26T11:34:33.556+02:00Hello Opher, it may also be understood as follows:...Hello Opher, it may also be understood as follows: there's no derived event but a detection of a composite event which is an entry event followed by an exit event of the same vehicle. The calculation of the highway fee, as well as the delivery to the vehicle of that fee, is the "business" logic associated to the composite event. This view does not see the delivery of the fee as an event but as part of the business logic. If we were to create an event that represented the composite event for other "listeners" to react then we would have a derived event. So a derived event represents a composite event with a single event... PatternStormnoreply@blogger.comtag:blogger.com,1999:blog-7831813422886730737.post-25294940678155278592012-09-25T10:56:51.338+02:002012-09-25T10:56:51.338+02:00Hi Opher,
to thoughts on that topic based on my p...Hi Opher,<br /><br />to thoughts on that topic based on my project experience<br /><br />(1) From a business perspective the semantics make a huge difference since the meaning of the actual event is something completely different<br />(2) From a technical perspective, I personally like to keep it the same as long as the functional aspects do not require a different handling which is commonly the result of the different semantics (e.g. how do you have to treat the event regarding to persistence requirements, etc.)<br /><br />One common approach for this is a generic implementation with an additional parameter for further processing in the event if there is a need for.<br /><br />Best regards,<br /><br />ChristophAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-7831813422886730737.post-65301740858884350622012-09-24T23:53:15.497+02:002012-09-24T23:53:15.497+02:00The difference should be distinguishable both sema...The difference should be distinguishable both semantically and computationally. In the case of a derived event, the computation should take a set of events as an input and produce a new event (and not a message). The other type, not being an event (an event's consequent?) may produce a message. Anonymousnoreply@blogger.com