by Kim Nevelsteen
Since its introduction in 1992, by author Neal Stephenson, the Metaverse concept has taken on many different meanings. To some the Metaverse means the convergence of augmented reality, virtual reality and physical world, including haptics and more [Dionisio, Burns III, & Gilbert, 2013]. To others it is a system of interconnected worlds accessible through a single user interface [Frey et al., 2008; Nevelsteen, in press]. Whichever definition is used, there are serious challenges to overcome before the Internet can be transformed into a 3D virtual space. Previous attempts to build the Metaverse have concentrated on a realism compared to the physical world, but scalability and interoperability remained unsolved. A Kickstarter project has been started to start the conversation pertaining to scalability and interoperability, rather than realism:
Virtual worlds on the massive multiplayer scale (MMOWs) have reached 100's of thousands simultaneous connected players [BigWorld, 2002], but there are still critical points of failure e.g., when players converge on a single area causing the number of interactions for a single area server or the communication overhead between multiple area servers to become unmaintainable. Various partitioning and interest management schemes have been researched for MMOWs [Yahyavi & Kemme, 2013], but several challenges remain (the reader is guided to Yahyavi and Kemme  for details).
According to Rehm, Goel, and Crespi , the concept of Internet of Things (IoT) has been recently been replaced by the concept of Cyber-Physical Systems. Rehm et al. believe that "virtual worlds can serve as platforms to facilitate the integration required by CPS [Cyber-Physical Systems]". In other words, using the "coextensive virtual world as a 'behind the scenes' resource for coordinating and managing devices and interaction in the physical space" [Greenhalgh, Izadi, Rodden, & Benford, 2001]. And, by extrapolation, they "conceive of a unified platform, the Metaverse, built on VW [virtual world] technologies that allow for the integration of technological, physical, and human elements of CPS [Cyber-Physical Systems]" i.e., using the Metaverse as a 'behind the scenes' resource for Cyber-Physical Systems.
To achieve scalability through adding resources, cloud computing and peer-to-peer (P2P) solutions are being considered in the domain of IoT), but research in the domain of MMOWs is more advanced, with running platforms utilizing partitioning schemes such as regionalization and replication in combination with interest management [Nevelsteen, Kanter, & Rahmani, in press].
Branton, Carver, and Ullmer  states that interoperability between web services is 'largely lacking' and Singhal et al.  state that the research community is only is beginning to develop architectures, technologies, and standards to support collaboration among multiple cloud systems. The only real solution to interoperability that is being proposed is standardization. For example, the MPEG-V [ISO/IEC JTC 1/SC 29, 2009] is a standard which outlines an architecture for interoperability between a virtual world (MMOWs) and the physical world (via IoT). In addition the standard aims to enable interoperability between virtual worlds by characterizing metadata for virtual world objects, so that objects can be migrated from one virtual world to another. MPEG-V has been drafted to support the Metaverse i.e., forming a system of interoperable interconnected virtual worlds. But, standardization is slow in creation and adoption, while also inhibiting progress. New ways need to be found to deal with interoperability.
Beyond, scalability and interoperability, there are still many problems left to solve related to the Metaverse e.g., interactivity, consistency, persistence, security and privacy, content generation and more. There is currently only one small workshop that deals with all the problems related to the Metaverse i.e., the International Workshop on Massively Multiuser Virtual Environment (http://mocca.uni.lu/mmve2016/), which is hosted by the ACM Multimedia Systems Conference. To gather interest in building a shared Metaverse framework, please checkout the Kickstarter project: https://www.kickstarter. com/projects/49217276/internet-2021-the-metaverse-internet-of-3d-virtual
Your support and input is highly valuable and appreciated.
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