# A Survey of the Real-Time Metaverse: Challenges and Opportunities +
## 7 Interoperability Standards
### OpenXR  
OpenXR is an open standard for VR and AR that aims to streamline the development of applications across different hardware platforms [228]. Khronos Group, a consortium of industry-leading companies, has developed OpenXR, which provides a unified framework for VR and AR runtime interfaces. This allows developers to write code that can run on various devices without tailoring their applications to each specific platform. OpenXR provides a set of standardized APIs (application programming interfaces) that sit between XR applications and the underlying hardware, effectively decoupling software from hardware [221]. By abstracting the hardware details, OpenXR significantly reduces the complexity and cost of developing cross-platform VR and AR experiences, fostering more significant innovation and broader adoption in the immersive technology space. The benefits of OpenXR extend beyond simplifying development. For end users, it ensures a more consistent and reliable experience across different VR and AR devices [229]. Since applications built with OpenXR can operate on multiple platforms, users are not limited to specific hardware when accessing their favorite VR and AR content. This interoperability also encourages competition among hardware manufacturers, as it levels the playing field and allows new entrants to support a rich content ecosystem without the barrier of proprietary software constraints. Ultimately, OpenXR plays a crucial role in the growth of the VR and AR industries by promoting a more open, inclusive, and efficient development environment. By abstracting the hardware details, OpenXR significantly reduces the complexity and cost of developing cross-platform VR and AR experiences, fostering greater innovation and broader adoption in the immersive technology space [230]. This streamlined approach enables developers to spend more time focusing on the content and user experience, rather than worrying about hardware compatibility and performance optimization across different platforms. For example, OpenXR enables developers to use the same application on Meta Quest, which runs on a mobile chipset, as they would on a high-end PC VR system, with OpenXR taking care of the specific hardware adaptations. In addition to simplifying development, OpenXR offers substantial benefits for end users. It ensures a more consistent and reliable experience across different VR and AR devices [231]. This is especially important as the hardware landscape for XR continues to diversify. With the rise of new devices, from standalone headsets like Meta Quest 3 to AR glasses from companies like Magic Leap and Apple [232], users have more options than ever before. Thanks to OpenXR, users are no longer restricted to specific hardware ecosystems when accessing their favorite VR and AR content. For example, a user who purchases an app for their Oculus Quest 3 can seamlessly transition to using the same app on Valve's Index VR or Windows Mixed Reality without losing any functionality or performance, as long as both platforms support OpenXR. This interoperability also encourages competition among hardware manufacturers [233], as it levels the playing field and allows new entrants to support a rich content ecosystem without the barrier of proprietary software constraints. Companies are incentivized to innovate in hardware design and performance rather than relying on walled gardens to retain users. For instance, smaller or newer VR/AR hardware companies that support OpenXR can leverage the existing library of OpenXR applications, thereby reducing the friction involved in building their ecosystem from scratch. Moreover, OpenXR promotes accessibility and inclusivity in the development and user communities [234]. For smaller development studios or individual creators, the costs of developing multiple versions of a VR/AR application for different platforms can be prohibitive.