V2/Concepts/Intro to Tag
Tag
A tag is an attribute of the sample. It is usually used as a way to identify where is the metrics are taken from (eg. device ID). It is also useful for labelling the data being sent, in order to perform operations on the data later, eg. filtering.
Example
Say you have a smart weighing scale at home. One possible way to represent the time series data for the device is as follows:
- Measurement
- Smart Weighing Scale
- Measurement code
- iot_weighingscale_v1
- Data
| tm_source | weight_kg |
|---|---|
| xxxxxxxxxxxxx | 70.1 |
| xxxxxxxxxxxxx | 70.4 |
| xxxxxxxxxxxxx | 69.4 |
tm_source represents when the reading was taken. In this case, weight_kg is the metric, and is sent everytime a weight is taken.
This is well and good, but what if there is another person who's using the weighing scale? One way to distinguish them apart is by adding an additional field, or tag, called person:
| tm_source | person | weight_kg |
|---|---|---|
| xxxxxxxxxxxxx | Sam | 70.1 |
| xxxxxxxxxxxxx | Susan | 55.2 |
| xxxxxxxxxxxxx | Sam | 70.4 |
Much better. But what if there are multiple weighing scales in the house? We can tell them apart by adding another tag:
| tm_source | room | person | weight_kg |
|---|---|---|---|
| xxxxxxxxxxxxx | bathroom | Sam | 70.1 |
| xxxxxxxxxxxxx | kitchen | Susan | 55.2 |
| xxxxxxxxxxxxx | kitchen | Sam | 70.4 |
So we end up with a measurement that has 2 tags (room, person) and 1 metric (weight_kg).
A more complete example can be as follows:
| tm_source | site_id | room | person | weight_kg | bodyfat | battery_level |
|---|---|---|---|---|---|---|
| xxxxxxxxxxxxx | 1547 | bathroom | Sam | 70.1 | 19.1 | 99 |
| xxxxxxxxxxxxx | 1547 | kitchen | Susan | 55.2 | 15.3 | 54 |
| xxxxxxxxxxxxx | 1547 | kitchen | Sam | 70.4 | 19.2 | 49 |
This example is admittedly contrived, but it serves as an example of how data can be modelled in Senfi.