## 3 IFC Interoperability, a Literature Review  
Table 1 collects the main studies available in the technical literature on IFC-based interoperability involving structural analysis and design problems, produced within the past ten years. It also depicts the contribution of the present study in this context and its novel aspects, such as the assessment of IFC 4 DTV, which has rarely been documented before. As previously stated, (see Section 2), this study used the model view definition SAV in different software environments to focus on the interoperability process specifically dedicated to structural analysis. Early studies dating back to 2008, carried out by [PERSON] and [PERSON] [27], on the horizontal interoperability of the most common IFC-compatible software, focused on the IFC 2x Add1 format and the Extended Geometric View MVD, showed that the IFC interface did not work as expected. Many cases of distortion or loss of information related to the geometry of the elements, such as the non-alignment of beams, columns, and walls, resulting in an incorrect connection between the elements, were observed. Other typical problems were related to the loss of attributes and properties, such as the change of materials, colours, and the artefact shape of the elements. Despite the evolution of the IFC format, switched from IFC 2x Add1 to IF C2x3, and the introduction of the additional MVD, namely, the Coordination View v2.0, the loss of data continued to exist, and other case studies showed that the problem related to the incorrect interpretation of the geometry of the elements and results was still widespread. One of the first trial studies was carried out by [PERSON] et al. [28] and focused on detailed benchmark tests using a small but complex building model that implemented IFC 2x3. Imperfect exchanges were observed due primarily to the lack of uniformity in the way the internal object schemas were mapped onto the IFC objects and properties. Reference BIM packages included Revit, ArchiCAD, Digital Project, Bentley Architecture, and Tekla Structures. A data exchange analysis between two of the most popular BIM software, Revit and Tekla, was presented by [PERSON] and [PERSON] [29]. Models were exchanged by using IFC CV 2.0, and a comparison was made in terms of data loss and misrepresentation of geometry and section types. The loss of data related to geometry, profile, and material was also reported by [PERSON] et al. [9], who tested horizontal and vertical interoperability between CAD software, such as Revit and ArchiCAD, and CAE software, such as AxisVM, in a bidirectional data exchange using IFC. [PERSON] [30] documented a study carried out in three different BIM authoring tools, i.e., AllPlan, Revit, and ArchiCAD; the geometry representation of the building in the structural analysis software was evaluated in terms of consistency and usability via two CAE software: RFEM and SCIA Engineer. Inconsistencies, such as data transfer losses or misinterpretations of linear elements, planar elements, and connectivity, were reported. [PERSON] [31] evidenced the lack of proper communication between BIM software and the open format IFC containing some practical deficiencies. The work was carried out to test the use of BIM in structural design and calculations using several commercial BIM software and structural BIM tools (S-BIM Tools) such as Revit, Robot Structural analysis, Rhinoceros, and Tekla structures. The application of interpreted information exchange (IIE) for engineering analyses was illustrated by [PERSON] and [PERSON] [32]. An explanatory platform was created to implement the structural analytical model, starting from the architectural model; the authors observed that despite the MVD standard (CV 2.0) being widely adopted by BIM-based software, most design/analysis software packages were not able to export structural MVDs. As a result, the geometry of the elements was subjected to changes, while other information such as the loads and the responses of the structure were not transferable.