Logic node expressions and syntax

Expression fundamentals

The Logic node uses the Navixy IoT Logic Expression Language, which is based on Java Expression Language (JEXL). All expressions must return a boolean value (true/false) for proper node operation.

Expression evaluation: Expressions are evaluated from left to right, and you can use parentheses to control the order of operations.

Basic syntax example:

CODE

condition1 && (condition2 || condition3 > condition4)

Available operators

Comparison operators

Operator	Description
`==`	Checks if two operands are equal. If operands are of different types, JEXL converts them to one if possible
`!=`	Checks for inequality of two operands. Returns true if operands are not equal
`<`	Checks that the left operand is smaller than the right operand
`<=`	Checks that the left operand is smaller or equal to the right operand
`>`	Checks that the left operand is larger than the right operand
`>=`	Checks that the left operand is larger or equal to the right operand

Logical operators

Operator	Description
`&&` or `and`	Logical AND - checks if two conditions are true. Returns true if both conditions are true
`\|\|` or `or`	Logical OR - checking for the truth of at least one of the two conditions
`!` or `not`	Logical NOT - converts the result of the condition to the opposite value

Pattern matching operators

Operator	Description
`=~`	Checks if the value of the left operand is in the set of the right operand. For strings, checks for regex pattern match
`!~`	Checks if the value of the left operand is not in the set of the right operand. For strings, checks for regex pattern mismatch
`=^`	Checks that the left string operand starts with the right string operand
`!^`	Checks that the left string operand doesn't start with the right string operand
`=$`	Checks that the left string operand ends with the right string operand
`!$`	Checks that the left string operand doesn't end with the right string operand

Expression examples

Basic condition examples

Equality checks:

CODE

value('lock_state', 0, 'valid') == 'sealed'
door_state_2 == 0

Inequality checks:

CODE

value('lock_state', 1, 'valid') != 'unknown'
avl_io_221 != null

Numeric comparisons:

CODE

value('humidity', 1, 'all') < 80
value('humidity', 1, 'all') <= 80
value('humidity', 0, 'valid') > 80
value('humidity', 0, 'valid') >= 80

Temperature monitoring:

CODE

value('temperature', 0, 'valid') > 75

This expression triggers when temperature exceeds 75 degrees, useful for overheating alerts.

Speed violation detection:

CODE

value('speed', 0, 'valid') > 80

This expression identifies when vehicles exceed 80 km/h speed limits.

Device health monitoring:

CODE

value('battery_voltage', 0, 'valid') < 11.5

This expression detects low battery conditions requiring maintenance attention.

Fuel level alerts:

CODE

value('fuel_level', 0, 'valid') < 20

This expression identifies when fuel levels drop below 20%, enabling proactive refueling.

Logical operator examples

AND operations:

CODE

value('temperature', 0, 'valid') > 15 && value('humidity', 0, 'valid') > 80
value('temperature', 0, 'valid') > 15 and value('humidity', 0, 'valid') > 80

OR operations:

CODE

temperature < 10 || humidity > 80
temperature < 10 or humidity > 80

NOT operations:

CODE

!condition
not condition

Pattern matching examples

Set membership:

CODE

value('lock_state', 0, 'valid') =~ ['locked','unlocked']
value('driver_name', 0, 'valid') !~ ['John', 'Steve']

String pattern matching:

CODE

driver_id =^ 'cc6f8216'
driver_id !^ 'cc6f8216'
value('engine_hours', 0, 'valid') =$ '1000'
value('driver_id', 0, 'valid') !$ '8b38851c3c68'

Complex multi-condition examples

After-hours speeding alert:

CODE

value('speed', 0, 'valid') > 60 && (value('current_hour', 0, 'valid') >= 18 || value('current_hour', 0, 'valid') <= 6)

This combines speed monitoring with time-based conditions for enhanced safety oversight during night shifts.

Comprehensive device diagnostics:

CODE

value('gps_satellites', 0, 'valid') >= 4 && value('battery_voltage', 0, 'valid') > 11.5 && value('signal_strength', 0, 'valid') > -80

This validates multiple device health parameters simultaneously to ensure reliable operation.

Driver safety monitoring:

CODE

value('harsh_braking', 0, 'valid') == true && value('driver_identified', 0, 'valid') == false

This identifies unsafe driving behavior when the driver isn't properly identified in the system.

Equipment maintenance scheduling:

CODE

value('engine_hours', 0, 'valid') > 250 && value('last_maintenance', 0, 'valid') > 30

This triggers maintenance alerts when engine hours exceed thresholds and maintenance is overdue.

Temperature range compliance:

CODE

value('cargo_temperature', 0, 'valid') < -18 || value('cargo_temperature', 0, 'valid') > 4

This detects when refrigerated cargo temperatures fall outside the acceptable range.

Expression complexity and parentheses

You can create complex expressions by combining multiple conditions with parentheses to control evaluation order:

Complex safety validation:

CODE

!driver_identified && (vibration_active || speed > 3)

Multi-parameter equipment check:

CODE

(value('oil_pressure', 0, 'valid') < 20 || value('coolant_temp', 0, 'valid') > 95) && value('engine_running', 0, 'valid') == true

Error handling scenarios

Scenario	Result	Flow Path	Attribute Value
Expression evaluates to `true`	Success	THEN connection	`true`
Expression evaluates to `false`	Success	ELSE connection	`false`
Referenced attribute is `null`	Treated as `false`	ELSE connection	`false`
Syntax error in expression	Treated as `false`	ELSE connection	`null`
Referenced attribute doesn't exist	Treated as `false`	ELSE connection	`null`

Practical implementation examples

Fleet temperature monitoring

Business requirement: Monitor refrigerated vehicles to ensure cargo temperature compliance

CODE

value('cargo_temperature', 0, 'valid') > 4 || value('cargo_temperature', 0, 'valid') < -18

THEN path: Send immediate alerts to dispatch, log compliance violations, trigger corrective actions
ELSE path: Continue normal processing for compliant temperatures, update status dashboards

Driver safety enforcement

Business requirement: Identify unsafe driving patterns during active shift hours

CODE

value('harsh_acceleration', 0, 'valid') == true && value('shift_active', 0, 'valid') == true

THEN path: Generate driver coaching reports, send safety notifications, log incidents
ELSE path: Process normal driving behavior data, update performance metrics

Predictive maintenance alerts

Business requirement: Detect potential equipment failures before they occur

CODE

value('engine_temperature', 0, 'valid') > 95 && value('oil_pressure', 0, 'valid') < 30

THEN path: Schedule maintenance appointments, send technician alerts, log diagnostic data
ELSE path: Continue routine monitoring, update equipment health dashboards

Geofence compliance monitoring

Business requirement: Ensure vehicles operate within authorized areas during business hours

CODE

(value('latitude', 0, 'valid') < 40.7489 || value('latitude', 0, 'valid') > 40.7589) && value('business_hours', 0, 'valid') == true

THEN path: Generate unauthorized location alerts, notify security, log violations
ELSE path: Continue normal operations logging, update location tracking