### Cloud-BIM Solutions and BIM Data  
BIM projects require multidisciplinary approaches and steady updates through professional collaborations. Cloud environments can ensure the real-time access and control of IFC files; project members and stakeholders can work together on a digital platform which allows the management, inspection and review of the 3D space and semantic data [9]. In fact, web and cloud BIM platforms leaning on a 3D viewer for the IFC model visualization and a database system are mostly composed of IFC information and visualized as a tree of objects depending on architecture classification [4; 13]. These platforms are free (or limited) web applications or Software-as-a-Service (SaaS) solutions, especially designed for multiple device access to a common cloud system. Although the actual panorama of cloud-BIM is strongly affected by the presence of fee-based solutions (e.g., Autodesk Bim 360 and Graphisoft BIMx), the number of free and open-source web applications are growing, also thanks to the increase of WebGL apps and web development [14]. Reliable solutions include BIMServer.center [16] and BIMServer [17]. The first is a free cross-platform for data exchange of IFC models, which is accessible from every device. In addition to the 3D model investigation, it includes a marketplace with stand-alone apps and plugins, allowing several analyses. Lately, the platform allows one to access the BIM project in Virtual Reality (VR) and Augmented Reality (AR) environments, unlocking a new level of accessibility and immersion. The second, BIMServer, is an open-source web platform (via browsers) reachable through a JavaScript server app that allows the management and sharing of BIM projects. It relies on an investigation and revision environment, as well as on a database and query system. Alongside the presence of these cloud-BIM solutions, another platform represents the perfect match between features, design stability, a user-friendly interface and source code accessibility: BIMData [18]. The BIMData web platform (SaaS licence) is probably the most interesting and flexible cloud solution for managing BIM projects in a smart environment (Figure 1). It includes three suites (free, professional, enterprise) where the differences principally concern cloud storage, the IFC editor, email support and Application Programming Interface (API) access. Inside the platform, IFC files reach complete accessibility, including the related semantic data. The 3D viewer allows investigation of the IFC objects' structures and properties and their edition (Figure 2). This feature is up to stable version 0.8.26; recent versions of free plan no longer have this function. Figure 1: BIMData page account. Sections: IFC model; localization; invitation for users and sources archive. One of the most important features of BIMData is the BIM Collaboration Format (BCF) option, which allows for the reporting of issues and the reviewing of data and file deformities. The access system was conceived to guarantee multiple invitations and permissions (guest, user, admin). The upload and cloud system of BIMData can host any file type associated with IFC digital models: e.g., images, PDFs and datasheets can be managed, consulted and updated inside the web environment. Behind the attention to detail and the clear and user-friendly interface, there is a precise developing work carried out via open-source programming languages; in fact, BIMData is principally based on VueJS (design system), JavaScript and XEOKIT, which is an open-source programming 3D toolkit (WebGL SDK) developed by XEOLABS [19,20] and designed for BIM and AEC. The BIMData team of developers are committed to sharing source codes, giving users complete access to the main viewer, the interface and the plugins design. In fact, the official website (bimdata.io, accessed on 23 August 2021) includes an important section referring to source code documentation and tutorials; through this section, all developers can access and modify/adapt BIMData codes and structure depending on specific needs.