Thing snapshots
AMTech Platform keeps track of last changes made to the properties of thing instances. The number of previous changes to store, and the frequency to store them, must be configured in the thing type as explained here. The number of snapshots to be stored for the property is the (observation limit) and the minimum time between two changes to create a new snapshot is the (observation frequency).
For instance, the following configuration keeps the last 100 updates that occurred to this supported property and the property will be updated with 5 minutes frequency (ignoring updates that happened more frequently)
The current value of the property is not included in the snapshots.
Each time a modification to a thing property is done, it is verified if the last snapshot for this field was done at least the time in observation frequency before. Use 0 to accept all modifications. Also, set the observation limit to say how many snapshots to store. The last ones are removed if the limit is reached.
This feature have two uses in AMTech Platform:
- Timeline view shows the stored snapshots and their modification time. Also the map include the last locations if the field has more than one snapshot.
- Observers allow to define constraints on the snapshots by using their average, minimum, maximum, count or sum.
