Compiling OpenSCENARIO 2.1 for Scenario-Based Testing in CARLA

Thoshitha Gamage; Lasanthi Gamage

cs.ROApr 7, 2026

Compiling OpenSCENARIO 2.1 for Scenario-Based Testing in CARLA

Authors: Thoshitha Gamage, Lasanthi Gamage

Organizations: Department of Computer Science, Southern Illinois University Edwardsville, Edwardsville, IL · Department of Computer Science, Webster University, Webster Groves, MO

Abstract

While the ASAM OpenSCENARIO 2.1 Domain-Specific Language (DSL) enables declarative, intent-driven authoring for Scenario-Based Testing (SBT), its integration into open-source simulators like CARLA remains limited by legacy parsers. We propose a multi-pass modern compiler architecture that translates the OpenSCENARIO 2.1 DSL directly into executable CARLA behaviors. The pipeline features an ANTLR4 frontend for Abstract Syntax Tree (AST) generation, a semantic middle-end, and a runtime backend that synthesizes deterministic py_trees behavior trees. Mapping the standardized domain ontology directly to CARLA's procedural API via a custom method registry eliminates the need for external logic solvers. A demonstrative multi-actor cut-in and evasive maneuver, selected from a wider suite of validated scenarios, confirms the compiler's ability to process concurrent actions, dynamic mathematical expressions, and asynchronous signaling. This framework establishes a functional baseline for reproducible, large-scale SBT, paving the way for future C++ optimizations to mitigate current Python-based computational overhead.

Figures & tables

Feature	OSC 1.3 (XML)	OSC 2.1 (DSL)
Format	Schema-based (XML)	Text-based DSL (EBNF)
Hierarchy	Storyboard $\rightarrow$ Act $\rightarrow$ Maneuver $\rightarrow$ Event $\rightarrow$ Action	Declarative, intent-driven structure
Logic	Trigger-based conditions	Full expressions, conditions, and logic
Parameterization	Parameters and catalogs	Native variables and reusable abstractions
Modularity	Limited reuse via catalogs	High modularity and composability
Behavior Modeling	Explicit action definitions	Actions + Modifiers + Conditions separation

Table 1: Comparison of OpenSCENARIO v1.3 (XML) and v2.1 (DSL)

Figure 1: The 3-stage OSC2 Execution Pipeline mapping DSL definitions to CARLA behaviors.

Category	Capability	Description	Implementation Method	Supported
Action Framework	Action lifecycle	Start, end, fail states	Behavior Tree status tracking	$\checkmark$
	Actor binding	Map actions to actors	Runtime execution context	$\checkmark$
	Composition	Sequential/parallel	Tree composites (serial/parallel)	$\checkmark$
	Duration handling	Time bounds	Parallel timeout wrappers	$\checkmark$
Movement	Move/drive/walk	Motion primitives	LocalPlanner/WaypointFollower	$\checkmark$
	Speed control	Adjust speed	PID longitudinal control	$\checkmark$

Table 2: Extended capability checklist aligned with OCS2, detailing supported actions, modifiers, and condition semantics within the implementation.

Panel of Figure 2 — Figure 2: Simulation state following the declarative initialization phase, captured from multiple perspectives.

Panel of Figure 3 — Figure 3: Phase 2 execution: The ego vehicle concurrently executing a lateral maneuver and a visual warning in response to the spatial trigger.

Panel of Figure 4 — Figure 4: Phase 5 execution: Both actors synchronize their deceleration profiles to halt safely, demonstrating precise spatial and temporal control.

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OSC2Runner: OpenSCENARIO 2.x Compliant High-Fidelity AV Simulation in CARLA

Thoshitha Gamage, Lasanthi Gamage

Southern Illinois University Edwardsville, Edwardsville, IL, USA · Webster University, St. Louis, MO, USA

Autonomous Driving Simulation

Open paper AskPDF arXiv

Scenario-Based Testing predominantly relies on the legacy ASAM OpenSCENARIO 1.x XML standard because existing continuous simulation frameworks lack native execution support for the recently matured v2.x Domain-Specific Language (DSL). Adapting legacy interpreters to evaluate v2.x logic introduces spatiotemporal drift, asynchronous event latencies, and artificial kinematic snapping. Addressing this execution gap, OSC2Runner introduces the first orchestration framework capable of natively mapping the OpenSCENARIO v2.x DSL to CARLA. The framework achieves this by formalizing scenario translation as a compilation pipeline through a multi-pass transpiler architecture. Bypassing static trajectory playback, the architecture synthesizes type-safe Abstract Syntax Trees directly into dynamic deterministic behavior trees (py_trees) natively mapped to CARLA's atomic APIs. Empirical validation in highly concurrent adversarial case studies demonstrates tick-by-tick determinism, exact spatial trigger evaluation, and 100.0 ms cross-actor blackboard synchronization. Kinematic analysis proves the strict adherence to continuous environmental boundaries. This architecture transitions Scenario-Based Testing from approximate behavioral interpretation to mathematically rigorous execution, establishing the deterministic backend required for co-simulation, hardware-in-the-loop testing, and automated LLM-driven generation pipelines.

Abstract

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