High-Level Architecture (HLA) is a standard for distributed simulation, enabling seamless integration across systems and organizations. Over the years, it has evolved through multiple revisions, each enhancing performance, usability, and adaptability. The latest version, HLA 4, (IEEE HLA 1516-2025) was officially approved in February 2025. HLA 4 sets a new benchmark for the future of distributed simulation, delivering security, scalability, robustness, extensibility, cloud and container readiness, full life-cycle support, and backward compatibility. This blog post takes a closer look at the benefits of HLA 4, highlighting its key innovations and the new opportunities it brings.
A Brief Introduction to HLA
HLA is an open international standard that enables seamless interoperability between simulation systems. It is widely used for training and analysis in aerospace, defense, and civilian applications. With HLA, operators of ground vehicles, ships, and aircraft can train together in complex, realistic scenarios. Command and control personnel can rehearse decision-making in simulated environments, while simulators from different vendors can be linked for joint training. Even astronauts can prepare for future missions using HLA-enabled simulations.
The Evolution of HLA
The HLA standard originated in the 1990s and was developed under the guidance of the U.S. Department of Defense as a successor to simulation standards like DIS (Distributed Interactive Simulation). It has since been adopted globally and refined through successive versions, with HLA 1.3 (IEEE HLA 1516-2000), and HLA Evolved (IEEE HLA 1516-2010) introducing key improvements such as better modularity, optimized data distribution, and enhanced time management. Now, HLA 4 is set to take interoperability and scalability to the next level, fulfilling the needs of defense, space, and civilian simulations.
Why Does HLA 4 Matter?
At its core, the latest iteration of HLA is still a standard designed to make simulation systems interoperable, avoid vendor lock-in, and enable the reuse of components and simulators. It supports the creation of modular simulation systems, reducing development costs, mitigating program risk, and extending the lifecycle of simulation programs.
HLA 4 maintains these core principles while evolving to meet modern needs, adapting to the demands of large-scale, multi-domain simulations. It introduces new capabilities that enhance interoperability, scalability, and efficiency. Whether enabling cloud-based training environments, improving multinational military exercises, or advancing digital twin capabilities, HLA 4 supports the next generation of simulation challenges.
What’s New in HLA 4?
Security
HLA 4 introduces secure authentication, ensuring only authorized personnel and systems can access training scenarios. This safeguards mission integrity and prevents data leaks, particularly in mission rehearsals and sensor or weapons training. Additionally, secure communication mechanisms prevent unauthorized eavesdropping.
Scalability
Modern training scenarios require large-scale, high-entity simulations, such as urban warfare exercises. HLA 4 adds scalability through improved support of elastic cloud. It also enhances Data Distribution Management (DDM) for greater scalability and more efficient filtering, allowing users to focus on critical areas during an exercise.
Robustness
Training exercises can be costly, so ensuring the uninterrupted operation of the simulation components is critical. New networking features, like the HLA 4 Federate Protocol, add better support for connection recovery, ensuring training can continue smoothly even in the event of network disruptions or system failures.
Extensibility
The HLA community has developed powerful, standardized data exchange models known as Federation Object Models (FOMs), incorporating best practices on how to describe your objects and interactions from numerous projects. HLA 4 makes it easier than ever to extend these FOMs with project-specific requirements, providing tailored simulation capabilities.
Cloud and Container Support
Deploying large-scale simulation environments has traditionally been complex. HLA 4 utilizes containerization to enable flexible, scalable, and self-healing training systems, streamlining both development and deployment.
Broader Technology Support
Modern simulation environments span a variety of programming languages and game engines. The new HLA 4 Federate Protocol facilitates native interoperability with C++, Java, JavaScript, Python, and more.
Backward Compatibility
Transitioning to HLA 4 is seamless, thanks to vendor-supported backward compatibility with previous HLA versions and other standards like DIS.
How can I work with HLA 4?
As adoption of the standard grows, Pitch remains committed to enabling full HLA 4 support across our entire product suite. You can already explore HLA 4 today: test new features using the preview functionality in pRTI, use the Visual OMT beta for HLA 4 modeling, and take advantage of preview features in Developer Studio to generate integration code for HLA 4 interoperability.
Now that HLA 4 is officially approved, Pitch’s focus is shifting from showing previews to full-fledged implementation. The first HLA 4 compliant releases of pRTI and Visual OMT are expected in Q2 2025, with Developer Studio following towards the end of 2025. To learn more, reach out via our contact form and stay informed by following our blog and social media channels.