Opinions on sensor / reading / alert database design

Question

I\'ve asked a few questions lately regarding database design, probably too many ;-) However I beleive I\'m slowly getting to the heart of the matter with my design and am s

Answer 1

Here are my two cents on the problem.

AlertType table holds all possible types of alerts. AlertName may be something like high temperate, low pressure, low water level, etc.

AlertSetup table allows for setup of alert thresholds from a sensor for a specific alert type. For example, TresholdLevel = 100 and TresholdType = 'HI' should trigger alert for readings over 100.

Reading table holds sensor readings as they are streamed into the server (application).

Alert table holds all alerts. It keeps links to the first reading that triggered the alert and the last one that finished it (FirstReadingId, LastReadingId). IsActive is true if there is an active alert for the (SensorId, AlertTypeId) combination. IsActive can be set to false only by reading going below the alert threshold. IsAcknowledged means that an operator has acknowledged the alert.

1. The application layer inserts the new reading into the Reading table, captures the ReadingId.

2. Then application checks the reading against alert setups for each (SensorId, AlertTypeId) combination. At this point a collection of objects {SensorId, AlertTypeId, ReadingId, IsAlert} is created and the IsAlert flag is set for each object.

3. The Alert table is then checked for active alerts for each object {SensorId, AlertTypeId, ReadingId, IsAlert} from the collection.

   • If the IsAlert is TRUE and there are no active alerts for the (SensorId, AlertTypeId) combination, a new row is added to the Alert table with the FirstReadingID pointing to the current ReadingId. The IsActive is set to TRUE, the IsAcknowledged to FALSE.

   • If the IsAlert is TRUE and there is an active alert for the (SensorId, AlertTypeId) combination, that row is updated by setting the LastReadingID pointing to the current ReadingId.

   • If the IsAlert is FALSE and there is an active alert for the (SensorId, AlertTypeId) combination, that row is updated by setting the IsActive FALSE.

   • If the IsAlert is FALSE and there are no active alerts for the (SensorId, AlertTypeId) combination, the Alert table is not modified.