Syntax Basics

OSC2 uses indentation-based syntax (similar to Python) to organize code blocks. Files use the .osc extension.

Comments

Use # for single-line comments:

# This is a comment
scenario my_scenario:
    # Indented comment
    do serial:
        car.drive()

File Structure

An OSC2 file consists of import declarations and top-level definitions:

# Imports (optional)
import osc.standard

# Top-level definitions: types, enums, structs, actors, scenarios, etc.
type my_type is ...
scenario my_scenario:
    ...

Imports

Use the import statement to reference other files:

import "path/to/file.osc"    # File path import
import osc.standard           # Standard library import

Keywords

OSC2 reserved keywords:

scenario actor action struct type enum do serial parallel one_of event keep extend inherits def import with is it var global cover call wait on until emit if default fall rise elapsed every sample hard only remove_default undefined as in and or not range list of record external SI unit bool int uint float string

Identifiers

Identifiers are case-sensitive and support Unicode characters. Use pipe symbols to include spaces:

my_variable: int
|my variable|: string

Scenario Structure

Scenarios are declared with the scenario keyword, using do to define behavior:

scenario my_scenario:
    ego: vehicle
    do serial:
        ego.drive(duration: 10s)

Behavior Composition

• `serial — Sequential execution (next starts after previous ends)
• parallel — Concurrent execution (all start at the same time)
• one_of — Selective execution (randomly picks one branch)

do serial:
    phase1: parallel(duration: 5s):
        car1.drive()
        car2.drive()
    phase2: serial:
        car1.drive(speed: 30kph)
        car2.drive(speed: 50kph)

Modifiers

Use with to add parameters and constraints to behaviors:

car.drive() with:
    speed(60kph)
    lane(1)
    keep(speed < 80kph)

Literals

42              # Integer
3.14159         # Float
true            # Boolean
"hello"         # String
10m             # Physical quantity (10 meters)
50kph           # Physical quantity (50 km/h)
[1..10]         # Range

Complete Example

import osc.standard

scenario highway_drive:
    ego: vehicle
    do serial:
        approach: parallel(duration: 10s):
            ego.drive with:
                speed(60kph)
                lane(1)
        cruise: parallel(duration: 30s):
            ego.drive with:
                speed(80kph)
                lane(1)