6. Sensor Data

In the WoTKit, sensor data consists of a timestamp followed by one or more named fields. There are a number of reserved fields supported by the WoTKit:

Name	Value Description
timestamp	the time that the sensor data was collected. This is a long integer representing the number of milliseconds from Jan 1, 1970 UTC. Optional; if not supplied, a server-supplied timestamp will be used.
sensor_id	the globally unique sensor id that produced the data.
sensor_name	the globally unique sensor name, in the form {username}.{sensorname}
lat	the current latitude location of the sensor in degrees (number). Needed for map visualizations.
lng	the current longitude location of the sensor in degrees (number). Needed for map visualizations.
value	the primary value of the sensor data collected (number). Needed for most visualizations.
message	a text message, for example a twitter message (text). Needed for text/newsfeed visualizations.

In addition to these reserved fields, additional fields can be added by updating the sensor fields in the WoTKit UI or sensor_fields in the API.

Note

* Python’s time.time() function generates the system time in seconds, not milliseconds.

To convert this to an integer in milliseconds use int(time.time()*1000). Using Java: System.currentTime().

6.1. Sending New Data

To send new data to a sensor, POST name value pairs corresponding to the data fields to the /sensors/{sensorname}/data URL.

There is no need to provide a timestamp since it will be assigned by the server. Data posted to the system will be processed in real time.

To send new data:

URL	http://wotkit.sensetecnic.com/api/sensors/{sensorname}/data
Privacy	Private
Format	not applicable
Method	POST
Returns	HTTP status code; No Response 201 (Created) if successful

example

curl --user {id}:{password} --request POST
-d value=5 -d lng=6 -d lat=7 'http://wotkit.sensetecnic.com/api/sensors/test-sensor/data'

6.2. Sending Bulk Data

To send a range of data, you PUT data (rather than POST) data into the system. Note that data PUT into the WoTKit will not be processed in real time, since it occurred in the past

• The data sent must contain a list of JSON objects containing a timestamp and a value.
• If providing a single piece of data, existing data with the provided timestamp will be deleted and replaced. Otherwise, the new data will be added.
• If providing a range of data, the list must be ordered from earliest to most recent timestamp. Any existing data within this timestamp range will be deleted and replaced by the new data.

To update data:

URL	http://wotkit.sensetecnic.com/api/sensors/{sensorname}/data
Privacy	Private
Format	JSON
Method	PUT
Returns	HTTP status code; No Response 204 if successful

Example of valid data:

[{"timestamp":"2012-12-12T03:34:28.626Z","value":67.0,"lng":-123.1404,"lat":49.20532},
{"timestamp":"2012-12-12T03:34:28.665Z","value":63.0,"lng":-123.14054,"lat":49.20554},
{"timestamp":"2012-12-12T03:34:31.621Z","value":52.0,"lng":-123.14063,"lat":49.20559},
{"timestamp":"2012-12-12T03:34:35.121Z","value":68.0,"lng":-123.14057,"lat":49.20716},
{"timestamp":"2012-12-12T03:34:38.625Z","value":51.0,"lng":-123.14049,"lat":49.20757},
{"timestamp":"2012-12-12T03:34:42.126Z","value":55.0,"lng":-123.14044,"lat":49.20854},
{"timestamp":"2012-12-12T03:34:45.621Z","value":56.0,"lng":-123.14215,"lat":49.20855},
{"timestamp":"2012-12-12T03:34:49.122Z","value":55.0,"lng":-123.14727,"lat":49.20862},
{"timestamp":"2012-12-12T03:34:52.619Z","value":59.0,"lng":-123.14765,"lat":49.20868}]

example

curl --user {id}:{password} --request PUT --data-binary @data.txt
'http://wotkit.sensetecnic.com/api/sensors/test-sensor/data'

where data.txt contains JSON data similar to the above JSON array.

6.3. Deleting Data

Currently you can only delete data by timestamp, where timestamp is in numeric or ISO form. Note that if more than one sensor data point has the same timestamp, they all will be deleted.

To delete data:

URL	http://wotkit.sensetecnic.com/api/sensors/{sensorname}/data/{timestamp}
Privacy	Private
Format	not applicable
Method	DELETE
Returns	HTTP status code; No Response 204 if successful

6.4. Raw Data Retrieval

To retrieve raw data use the following:

URL	http://wotkit.sensetecnic.com/api/sensors/{sensor-name}/data?{query-params}
Privacy	Public or Private
Format	json
Method	GET
Returns	On success, OK 200 with a list of timestamped data records.

The query parameters supported are the following:

Name	Value Description
start	the absolute start time of the range of data selected in milliseconds. (Defaults to current time.) May only be used in combination with another parameter.
end	the absolute end time of the range of data in milliseconds
after	the relative time after the start time, e.g. after=300000 would be 5 minutes after the start time (Start time MUST also be provided.)
afterE	the number of elements after the start element or time. (Start time MUST also be provided.)
before	the relative time before the start time. E.g. data from the last hour would be before=3600000 (If not provided, start time default to current time.)
beforeE	the number of elements before the start time. E.g. to get the last 1000, use beforeE=1000 (If not provided, start time default to current time.)
reverse	true: order the data from newest to oldest; false (default):order from oldest to newest

Note

These queries looks for timestamps > “start” and timestamps <= “end”

6.5. Formatted Data Retrieval

To retrieve data in a format suitable for Google Visualizations, we support an additional resource for retrieving data called the dataTable.

URL	http://wotkit.sensetecnic.com/api/sensors/{sensor-name}/dataTable?{query-params}
Privacy	Public or Private
Format	json
Method	GET
Returns	On success, OK 200 with a list of timestamped data records.

In addition to the above query parameters, the following parameters are also supported:

tqx	A set of colon-delimited key/value pairs for standard parameters, defined here.
tq	A SQL clause to select and process data fields to return, explained here.

Note

When using tq sql queries, they must be url encoded. When using tqx name/value pairs, the reqId parameter is necessary.

For instance, the following would take the “test-sensor”, select all data where value was greater than 20, and display the output as an html table.

example

curl --user {id}:{password} http://wotkit.sensetecnic.com/api/sensors/test-sensor/
dataTable?tq=select%20*%20where%20value%3E20&reqId=1&out=html

6.6. Aggregated Data Retrieval

Aggregated data retrieval allows one to receive data from multiple sensors, queried using the same parameters as when searching for sensors or sensor data. The following parameters may be added to the /data url:

• scope

• tags

• private (deprecated, use visibility instead)

• visibility

• text

• active

• start

• end

• after

• afterE

• before

• beforeE

• orderBy

  • sensor: which groups data by sensor_id
  • time (default): which orders data by timestamp, regardless of the sensor it comes from.

To receive data from more that one sensor, use the following:

URL	http://wotkit.sensetecnic.com/api/data?{query-param}={query-value}&{param}={value}...
Privacy	Public or Private
Format	json
Method	GET
Returns	On success, OK 200 with a list of timestamped data records.

example

curl --user {id}:{password}
"http://wotkit.sensetecnic.com/api/data?subscribed=all&beforeE=20&orderBy=sensor"