MODEL Syntax and Components

Why Define a Schema?

Models transform scattered MQTT data into structured, predictable JSON. Instead of parsing raw payloads in your application, you define once how data should look—and Coreflux handles the rest.

Like a form that fills itself out. You define what fields the form should have (temperature, humidity, timestamp), and the model automatically grabs the latest values from different sources whenever it needs to publish.

When to Use This Reference

Use this page when you need to:

Define field types for your model (STRING, INT, DOUBLE, etc.)
Pull values from multiple MQTT topics into a single output
Calculate or transform values inline
Control when your model publishes using triggers

Basic Model Syntax

Every model follows this structure:

DEFINE MODEL <ModelName> WITH TOPIC "<output/topic>"
    ADD <FIELD_TYPE> "<field_name>" WITH <data_source> [AS TRIGGER]
    ADD <FIELD_TYPE> "<field_name>" WITH <data_source>
    ...

Components

ModelName

string

required

Unique identifier for the model. Use descriptive names like SensorReading, EquipmentStatus, ProductionRecord.

WITH TOPIC

string

required

The MQTT topic where the model’s JSON output will be published. Supports wildcards for multi-instance models.

FIELD_TYPE

type

required

One of: STRING, INT, DOUBLE, BOOL, ARRAY, OBJECT

AS TRIGGER

modifier

Optional. Marks this field as the trigger—the model publishes only when this field’s source topic updates.

Trigger Mechanism

The AS TRIGGER modifier controls when your model publishes. Without it, you’d flood your broker with updates every time any source topic changes.

Like a doorbell that takes a photo. The model waits quietly until the trigger topic “rings,” then takes a snapshot of all fields and publishes the complete picture. No ring, no photo.

DEFINE MODEL TriggeredModel WITH TOPIC "output/triggered"
    ADD STRING "equipment_id" WITH TOPIC "equipment/id"
    ADD STRING "status" WITH TOPIC "equipment/status" AS TRIGGER
    ADD INT "runtime" WITH TOPIC "equipment/runtime"
    ADD STRING "timestamp" WITH TIMESTAMP "UTC"

Behavior:

Model publishes only when equipment/status changes
Changes to equipment/id or equipment/runtime alone do not trigger publication
All field values are fetched at trigger time

No Trigger Specified

If no field has AS TRIGGER, the model acts as a template. You must publish it explicitly using PUBLISH MODEL from an Action.

Learn how to publish models on-demand in Publishing Models.

Multiple Data Sources, Single Trigger

You can pull data from many topics but trigger on just one:

DEFINE MODEL MultiSourceModel WITH TOPIC "output/multi"
    ADD STRING "sensor_a" WITH TOPIC "sensors/a/value"
    ADD STRING "sensor_b" WITH TOPIC "sensors/b/value"
    ADD STRING "sensor_c" WITH TOPIC "sensors/c/value" AS TRIGGER
    ADD STRING "timestamp" WITH TIMESTAMP "UTC"

Only publishes when sensor C updates, but includes current values from sensors A and B.

Field Types

Each field in your model has a type that determines how the value is serialized to JSON.

STRING

Text data of any length:

ADD STRING "sensor_id" WITH "TEMP001"
ADD STRING "status" WITH TOPIC "equipment/status"
ADD STRING "timestamp" WITH TIMESTAMP "UTC"

INT

Whole numbers (integers):

ADD INT "count" WITH 0
ADD INT "runtime_hours" WITH TOPIC "equipment/runtime"
ADD INT "total" WITH (GET TOPIC "passed" + GET TOPIC "failed")

DOUBLE

Decimal numbers (floating-point):

ADD DOUBLE "temperature" WITH 23.5
ADD DOUBLE "efficiency" WITH TOPIC "metrics/efficiency"
ADD DOUBLE "percentage" WITH (GET TOPIC "actual" AS DOUBLE / GET TOPIC "target" AS DOUBLE * 100)

BOOL

Boolean values (true/false):

ADD BOOL "enabled" WITH TRUE
ADD BOOL "maintenance_required" WITH TOPIC "equipment/needs_maintenance"
ADD BOOL "is_valid" WITH (GET TOPIC "value" > 0)

ARRAY

JSON arrays:

ADD ARRAY "readings" WITH TOPIC "sensors/batch/readings"
ADD ARRAY "tags" WITH ["production", "line1", "active"]

OBJECT

Nested JSON objects. Fields indented one level deeper than ADD OBJECT become properties of the sub-object. When the indentation returns to the parent level, subsequent fields belong to the parent again.

ADD OBJECT "metadata"
    ADD STRING "location" WITH "Building A"
    ADD INT "floor" WITH 3

Produces a nested structure in the JSON output:

{
  "metadata": {
    "location": "Building A",
    "floor": 3
  }
}

Indentation must be consistent throughout the model. Use either tabs or spaces — mixing them causes parsing errors.

Data Sources

Fields can pull values from several sources. Mix and match as needed.

Static Values

Fixed values that never change—useful for metadata, units, or default settings:

DEFINE MODEL StaticExample WITH TOPIC "output/static"
    ADD STRING "unit" WITH "celsius"
    ADD INT "default_threshold" WITH 100
    ADD DOUBLE "conversion_factor" WITH 1.8
    ADD BOOL "enabled" WITH TRUE
    ADD STRING "location" WITH "Factory Floor A"

Topic Data

Pull live values from other MQTT topics. The value is fetched at publish time, not when the model is defined.

DEFINE MODEL TopicExample WITH TOPIC "output/dynamic"
    ADD DOUBLE "temperature" WITH TOPIC "sensors/raw/temperature"
    ADD STRING "status" WITH TOPIC "equipment/current/status" AS TRIGGER
    ADD INT "count" WITH TOPIC "production/count"

Example: If sensors/raw/temperature currently holds 23.5, the model’s temperature field will be 23.5 when it publishes. If the value changes to 24.0 before the next publish, the model will output 24.0.

Timestamps

Built-in timestamp generation—no external time source needed:

ADD STRING "timestamp" WITH TIMESTAMP "UTC"      // "2025-10-25T14:30:15Z"
ADD STRING "iso_time" WITH TIMESTAMP "ISO"       // ISO 8601 format
ADD INT "unix_time" WITH TIMESTAMP "UNIX"        // 1729864215
ADD INT "unix_ms" WITH TIMESTAMP "UNIX-MS"       // Milliseconds since epoch

Calculated Values

Perform inline math using topic data:

DEFINE MODEL CalculatedExample WITH TOPIC "output/calculated"
    ADD DOUBLE "efficiency" WITH (GET TOPIC "produced" AS DOUBLE / GET TOPIC "target" AS DOUBLE * 100)
    ADD INT "total" WITH (GET TOPIC "passed" + GET TOPIC "failed")
    ADD DOUBLE "fahrenheit" WITH (GET TOPIC "celsius" AS DOUBLE * 9 / 5 + 32)
    ADD DOUBLE "average" WITH ((GET TOPIC "val1" + GET TOPIC "val2" + GET TOPIC "val3") / 3)

Always use AS DOUBLE or AS INT when performing mathematical operations to ensure correct type handling.

Conditional Values

Dynamic values based on conditions:

DEFINE MODEL ConditionalExample WITH TOPIC "output/conditional"
    ADD STRING "status" WITH IF (GET TOPIC "value" > 80) THEN "HIGH" ELSE "NORMAL"
    ADD STRING "quality" WITH IF (GET TOPIC "defects" = 0) THEN "PASS" ELSE "FAIL"
    ADD INT "priority" WITH IF (GET TOPIC "severity" EQUALS "CRITICAL") THEN 1 
                            ELSE IF (GET TOPIC "severity" EQUALS "HIGH") THEN 2 
                            ELSE 3

Wildcard Topics

Multi-Instance Models

Use + wildcards to create models that handle multiple instances automatically:

DEFINE MODEL MultiInstanceModel WITH TOPIC "sensors/+/formatted"

Matches:

sensors/temp001/formatted
sensors/pressure002/formatted
sensors/humidity003/formatted

Each unique topic creates a separate model instance.

JSON Reception with Wildcards

When JSON arrives at a wildcard topic, the broker “explodes” it into individual topics:

DEFINE MODEL MaterialData WITH TOPIC "Process/+/+/Material/Content"

When JSON arrives at Process/Machine/33/Material/Content:

{"MaterialID": 132323, "Name": "Peppers", "Quantity": 21}

Explodes to:

Process/Machine/33/Material/Content/MaterialID → 132323
Process/Machine/33/Material/Content/Name → Peppers
Process/Machine/33/Material/Content/Quantity → 21

Complete Examples

Equipment Status
Production Record

This model aggregates equipment data from multiple topics into a single, structured output. It triggers whenever the status changes.

DEFINE MODEL EquipmentStatus WITH TOPIC "equipment/status/formatted"
    ADD STRING "equipment_id" WITH TOPIC "equipment/current/id"
    ADD STRING "status" WITH TOPIC "equipment/current/status" AS TRIGGER
    ADD INT "runtime_hours" WITH TOPIC "equipment/current/runtime"
    ADD DOUBLE "efficiency" WITH TOPIC "equipment/current/efficiency"
    ADD BOOL "maintenance_required" WITH TOPIC "equipment/current/maintenance_flag"
    ADD STRING "last_update" WITH TIMESTAMP "UTC"
    ADD STRING "location" WITH "Factory Floor A"

Output:

{
  "equipment_id": "PUMP001",
  "status": "RUNNING",
  "runtime_hours": 1250,
  "efficiency": 87.5,
  "maintenance_required": false,
  "last_update": "2025-10-25T14:30:15Z",
  "location": "Factory Floor A"
}

This model calculates efficiency metrics inline. It triggers when the quantity updates, capturing a snapshot of the production run.

DEFINE MODEL ProductionRecord WITH TOPIC "production/records/completed"
    ADD STRING "batch_id" WITH TOPIC "production/current/batch_id"
    ADD STRING "product_code" WITH TOPIC "production/current/product_code"
    ADD INT "quantity_produced" WITH TOPIC "production/current/quantity" AS TRIGGER
    ADD INT "quantity_target" WITH TOPIC "production/current/target"
    ADD DOUBLE "efficiency_percent" WITH (GET TOPIC "production/current/quantity" AS DOUBLE / GET TOPIC "production/current/target" AS DOUBLE * 100)
    ADD STRING "operator" WITH TOPIC "production/current/operator"
    ADD STRING "completion_time" WITH TIMESTAMP "UTC"

Output:

{
  "batch_id": "BATCH-2025-1025",
  "product_code": "PRD-A1234",
  "quantity_produced": 850,
  "quantity_target": 1000,
  "efficiency_percent": 85.0,
  "operator": "John Smith",
  "completion_time": "2025-10-25T16:45:30Z"
}

Best Practices

Use Consistent Field Naming

Establish naming conventions and follow them across all models:

// Good - consistent across models
ADD STRING "timestamp"
ADD STRING "sensor_id"
ADD STRING "equipment_id"

// Avoid - inconsistent
ADD STRING "time_stamp"
ADD STRING "sensorID"
ADD STRING "equip_ID"

Always Type Cast in Calculations

Explicit type casting prevents errors and ensures predictable results:

// Good
ADD DOUBLE "efficiency" WITH (GET TOPIC "produced" AS DOUBLE / GET TOPIC "target" AS DOUBLE * 100)

// Risky - implicit type handling
ADD DOUBLE "efficiency" WITH (GET TOPIC "produced" / GET TOPIC "target" * 100)

Include Essential Context

Always include fields that help downstream consumers understand the data:

Identification fields (IDs, names)
Timestamps
Units of measurement
Status or quality indicators

Choose Triggers Carefully

Trigger on the primary data field, not metadata:

// Good - trigger on the main measurement
ADD DOUBLE "value" WITH TOPIC "sensors/temperature" AS TRIGGER

// Bad - triggers too frequently or unpredictably
ADD STRING "timestamp" WITH TIMESTAMP "UTC" AS TRIGGER

Quick Start

Developing and Managing Coreflux

Coreflux MQTT Broker

LoT Language

Product Updates

Why Define a Schema?

When to Use This Reference

Basic Model Syntax

Components

Trigger Mechanism

No Trigger Specified

Multiple Data Sources, Single Trigger

Field Types

STRING

INT

DOUBLE

BOOL

ARRAY

OBJECT

Data Sources

Static Values

Topic Data

Timestamps

Calculated Values

Conditional Values

Wildcard Topics

Multi-Instance Models

JSON Reception with Wildcards

Complete Examples

Best Practices

Next Steps

Publishing Models

Model Examples

​Why Define a Schema?

​When to Use This Reference

​Basic Model Syntax

​Components

​Trigger Mechanism

​No Trigger Specified

​Multiple Data Sources, Single Trigger

​Field Types

​STRING

​INT

​DOUBLE

​BOOL

​ARRAY

​OBJECT

​Data Sources

​Static Values

​Topic Data

​Timestamps

​Calculated Values

​Conditional Values

​Wildcard Topics

​Multi-Instance Models

​JSON Reception with Wildcards

​Complete Examples

​Best Practices

​Next Steps

Publishing Models

Model Examples

Why Define a Schema?

When to Use This Reference

Basic Model Syntax

Components

Trigger Mechanism

No Trigger Specified

Multiple Data Sources, Single Trigger

Field Types

STRING

INT

DOUBLE

BOOL

ARRAY

OBJECT

Data Sources

Static Values

Topic Data

Timestamps

Calculated Values

Conditional Values

Wildcard Topics

Multi-Instance Models

JSON Reception with Wildcards

Complete Examples

Best Practices

Next Steps