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title Complete sensor data processing
category Example
version 2.0.0
last_updated 2026-08-17
description Validated LoT for JSON sensors — action, model, rule, and optional OpenSearch

Complete sensor data processing

Official docs: LoT introduction · Working with JSON · Alarms

A concrete line you can deploy. Raw JSON arrives on sensors/+/raw. The action extracts fields (1-based topic position), publishes a collapsed model, and raises an alarm when temperature is out of range. A rule locks alerts/#. An optional OpenSearch route indexes the validated JSON.

The previous version of this page used WHILE, JSON.stringify, 0-based TOPIC POSITION, and an OpenSearch ADD MAPPING / MQTT_CONFIG that the parser does not accept. Those constructs are gone.

1. Model

DEFINE MODEL ValidatedSensor COLLAPSED
    ADD STRING "sensor_id"
    ADD DOUBLE "temperature"
    ADD DOUBLE "pressure"
    ADD STRING "quality"
    ADD STRING "timestamp"

2. Action

DEFINE ACTION ProcessSensorRaw
ON TOPIC "sensors/+/raw" DO
    SET "sensor_id" WITH TOPIC POSITION 2
    SET "temperature" WITH (GET JSON "temperature" IN PAYLOAD AS DOUBLE)
    SET "pressure" WITH (GET JSON "pressure" IN PAYLOAD AS DOUBLE)
    SET "quality" WITH "ok"
    IF {temperature} < -50 OR {temperature} > 150 THEN
        SET "quality" WITH "bad_temperature"
        PUBLISH TOPIC "alerts/" + {sensor_id} + "/temperature" WITH {temperature}
    PUBLISH MODEL ValidatedSensor TO "sensors/validated/" + {sensor_id} WITH
        sensor_id = {sensor_id}
        temperature = {temperature}
        pressure = {pressure}
        quality = {quality}
        timestamp = TIMESTAMP "UTC"

For sensors/oven-7/raw, position 2 is oven-7.

3. Rule

DEFINE RULE AlertsPublish WITH PRIORITY 20 FOR Publish TO TOPIC "alerts/#"
    IF USER HAS "AllowedSystemAlerts" OR USER IS "root" THEN
        ALLOW
    ELSE
        DENY

4. Optional index

DEFINE ROUTE SensorIndex WITH TYPE OPENSEARCH
    ADD OPENSEARCH_CONFIG
        WITH BASE_URL GET ENV "OPENSEARCH_URL"
        WITH USERNAME GET ENV "OPENSEARCH_USER"
        WITH PASSWORD GET SECRET "OPENSEARCH_PASSWORD"
        WITH USE_SSL true
    ADD EVENT IndexValidated
        WITH SOURCE_TOPIC "sensors/validated/+"
        WITH QUERY "CLEAN:{index: sensor-validated; body: {value.json}}"

Try it

Publish to sensors/oven-7/raw:

{"temperature": 25.5, "pressure": 101.3}

Expect sensors/validated/oven-7 as one JSON object. Publish {"temperature": 200, "pressure": 101.3} and also expect alerts/oven-7/temperature.

Uploadable notebook-free copies: ProcessSensorRaw.lot, ValidatedSensor.lot

Related: Factory line with a PLC, Edge to cloud and database

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