###### Abstract
Within the E-RIHS RI specifically, different tools and services are offered to researchers to deal with interaction in 3D spaces (virtual or physical), including the scientific visualization and presentation of 3D/4D data targeting the heritage sector. Their deployment in different facilities, and their use in public contexts and among remote researchers, can provide massive and valuable interaction records to be collected, studied, analyzed and investigated among RI nodes. Specialized capture tools can equip interactive applications to collect session records in remote server nodes, offering scientific communities access to dedicated hubs with associated web services for advanced analysis. Capturing such data in remote locations (including worldwide scenarios) and collecting such records over internet connections in dedicated hubs already presents several challenges. Advanced head-mounted displays (HMDs), eye tracking devices, brain-computer interface (BCI) headsets and motion tracking equipment, as well as wearable sensors or devices, may in fact require complex attributes in order to perform in-depth or ad hoc interaction analyses. Within H2 IOSC, the pilot, \"Immersive Analytics and Spatial Interfaces \", has the objective of designing and creating open-source immersive analytics (IA) cross-domain services to capture, process and inspect interaction data, using innovative interfaces and novel visualization models for XR inspection. Another goal of the pilot is to explore collaborative, online XR spaces, enabling remote analysts to discuss the captured data records and interaction patterns together. Web technologies allow us to craft complex and rich applications accessible through common browsers universally, without any installation required. Advancements within Web3D nowadays allow us to interact with and explore complex 3D environments, also through the use of immersive devices (via WebXR). These technologies can be used to access rich, immersive spaces but introduce new challenges related to performance, network bottlenecks and interface design. Web3D IA tools are in fact still quite new in the literature and present several challenges, especially when combining such solutions with fully immersive presentations (WebXR) and synchronous collaborative spaces (collaborative IA). In this paper, we present the first results of the H2 IOSC pilot \"Immersive Analytics and Spatial Interfaces\": an open-source web-based pipeline offering open-source tools and services to capture, process and inspect (immersively and collaboratively) recorded interactive sessions. The main contributions of our presented work are as follows. * A fully web-based, collaborative, modular, open-source pipeline to capture, process and inspect remote interactive sessions. The pipeline components can be deployed on single or multiple dedicated hubs. * A scalable and flexible capture service designed and developed to allow remote nodes to request session recording with custom attributes, also offering an accessible REST API for easy integration in other platforms, pilots or federated scenarios (Section 3.1). * An advanced WebXR immersive analytics tool (\"_Merkhet_\") to inspect records and data aggregates collected on remote hubs (Section 3.3), offering (A) spatial interfaces and elements to access, visualize and annotate spatio-temporal data records and aggregates, using immersive VR or augmented/mixed reality devices; (B) synchronous collaboration among multiple online analysts to discuss volumetric data records/aggregatestogether; (C) cross-device inspection using mobile devices, desktop devices and XR devices, through a standard web browser. * A suite of web-based services to develop analytics workflows, which will allow us first to examine and filter incoming raw data (Section 3.2) and then process the data using machine learning models. This stage is also designed to integrate novel encoding models specifically targeting massive data.