# Special Events

## Metadata

The metadata consists of the columns

* **Id**, is the id of the MQTT message in which the event was transmitted
* **Inserted**, the time it was inserted into the database
* **Size**, data size of the event
* **Thing**, id or name of the machine which generated the data
* **Timestamp**, timestamp describing the event
* **Type**, name/type of the event

These columns are contained in every event schema and are used to connect the different event schemas. \
The metadata events contain the collective of all metadata regardless of the event schema they actually belong to.

## Senseforce client state

The SF client state events contain information about the state of the edge component.

* **Reason**, this attribute isn't used at the moment.
* **State**, shows the status changes (connected/disconnected) of the according to SF edge.
* **Status code**, shows some information as **State** but in binary format (1/0).

## Senseforce messages

The SF message events contain information about the data included in the messages which were sent by the edge component.

* **Inserted events**, is the number of events that where included in the message with the given **Id** and inserted into the database. Each event is stored in a single row in the database.
* **Rejected events**, is the number of events that where included in the message with the given **Id** and rejected because of a violation against the event schema definition.
* **Compressed size**, is the size of the compressed message given in bytes.
* **Uncompressed size**, is the size of the uncompressed message given in bytes.
* **Compression ratio**, is the ratio between uncompressed and compressed size given by $$compression\_ratio  = compressed\_size/uncompressed\_size$$ 
* **Space savings**, is the data amount saved due to the compression. $$space\_savings = 1-uncompressed\_size/compressed\_size$$