aSHET

aSHET is a modular open-source software framework designed for developing and running hybrid simulations of complex, adaptive systems. The framework supports a mix of agent-based models, discrete-event processes, and continuous-time dynamics within a single coherent environment. It emphasizes reproducibility, extensibility, and interoperability with data pipelines and visualization tools.

Origin and development: The project emerged in the early 2020s from a collaboration among universities and research labs aiming to standardize simulation workflows for urban systems and infrastructure. The name aSHET is used in the project repository and literature to denote the Adaptive Hybrid Environment Toolkit (variations exist). The core team maintains a public repository and a reference implementation, with community-contributed adapters for external data sources and models.

Architecture: The framework comprises a core simulation engine, a component registry, and an event-driven messaging layer. Simulation components include agents, environment models, sensors and actuators, and analysis modules. It supports multi-scale time steps, parallel execution on CPUs/GPUs, and cloud deployment. A domain-specific language or configuration files allow users to assemble models and define experiments, while an API enables scripting in Python or other languages.

Applications: aSHET has been applied to traffic and mobility planning, energy-grid resilience, disaster-response simulations, and supply-chain risk assessment. It is also used in education and research to compare policy scenarios under uncertainty.

Reception and limitations: Proponents highlight its modularity, open architecture, and emphasis on reproducibility. Critics note a steep learning curve and performance overhead compared with specialized tools. Ongoing development focuses on scalability, standard data interfaces, and better integration with optimization and machine-learning workflows.