OpenSCENARIO 2.0 Parser (Semantic Extension)

A Python-based OpenSCENARIO 2.0 parser built on a fork of CARLA’s
scenario_runner, extended with early semantic validation and a
domain-aligned intermediate representation (IR).

The parser goes beyond syntax and validates scenarios against the
OpenSCENARIO 2.0 domain model (actors, actions, physical units, scopes),
making it suitable for static analysis, filtering, and matching of
scenarios.

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Key Features

• ANTLR4-based OpenSCENARIO 2.0 frontend
• Domain-aware actor / action / modifier validation
• Canonical symbols and actor-aware scope resolution
• Physical units & dimension checking (time, length, speed, …)
• Multi-stage pipeline: AST → IR → lowered IR
• Early rejection of semantically invalid scenarios

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Usage

from osc2_parser.parser import OSCProgram

osc_file = "change_lane.osc"
osc_prefix = "osc2_parser/osc/"
prog = OSCProgram(osc_path=osc_prefix + osc_file).compile()

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Quick API Overview

prog = OSCProgram(...).compile()

compile() returns a CompiledOSC object exposing the validated scenario via
a small, stable API:

prog.constraints_by_scenario

Structured, per-scenario representation preserving:

• actor instances and their domain types
• block hierarchy (serial / parallel), labels, and durations
• validated actions and modifiers
• typed physical values with explicit units

prog.calls

Flattened list of semantically validated action calls
(derived from constraints_by_scenario), intended for downstream
analysis, filtering, or matching.

prog.min_lanes

Inferred minimum lane requirement of the scenario.

prog.block_durations

Mapping from block labels to validated time durations.

prog.validation_result, prog.validation_errors

Outcome of semantic validation against the OpenSCENARIO 2.0 domain model.

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Compilation Output (Structure)

{
  "<scenario>": {
    "actors": {
      "ego_vehicle": {"type": "vehicle"}
    },
    "blocks": [
      {
        "type": "parallel",
        "label": "get_ahead",
        "duration": {"value": 15, "unit": "second"},
        "calls": [
          {
            "actor": "ego_vehicle",
            "action": "drive",
            "action_args": {
              "duration": {"value": 12, "unit": "second"}
            },
            "modifiers": [...]
          }
        ],
        "children": [...]
      }
    ],
    "calls_flat": [
      {
        "actor": "ego_vehicle",
        "action": "drive",
        "action_args": {...},
        "modifiers": [...],
        "block_label": "get_ahead",
        "block_type": "parallel"
      }
    ]
  }
}

All actions, parameters, and physical values appearing in this structure are
semantically validated and type-safe.

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Scope

• Grammar: OpenSCENARIO 2.0 (unchanged)
• Focus: static semantic correctness, not runtime execution
• Designed as a foundation for downstream analysis and matching pipelines

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Background

Developed as part of a master’s thesis on semantic validation, filtering, and
matching of OpenSCENARIO 2.0 scenarios.