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:

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:

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

Inequality checks:

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

Numeric comparisons:

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

Temperature monitoring:

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

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

Speed violation detection:

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

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

Device health monitoring:

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

This expression detects low battery conditions requiring maintenance attention.

Fuel level alerts:

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

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

Logical operator examples

AND operations:

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

OR operations:

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

NOT operations:

!condition
not condition

Pattern matching examples

Set membership:

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

String pattern matching:

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:

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:

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:

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:

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:

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:

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

Multi-parameter equipment check:

(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

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

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

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

(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