**4. Discussion**

Countries like China, the UK, Canada, South Korea, Germany, the USA, Australia and Italy are among the top publishers of both BIM global and BIM in universities. The geographic location plays a major role in the composition of most of the clusters. The UK's cluster is larger than more than six countries outside of the European continent combined. In addition, China is the leader in research about BIM within the Asian continent. The collaborating work of authors shapes the bibliometric map of BIM through numerous parameters, while citation network analysis of the cited references indicates a wide range of subjects in this field of research such as computer science, engineering, business, managemen<sup>t</sup> and accounting. These di fferent subjects show the diversity of this research area. The keywords analysis provided a list of diverse words related to themes like architectural design, construction management, interoperability, lean construction, virtual reality, visualization, robotics and sustainability development. The extensive amount of data that is generated to improve the facilities managemen<sup>t</sup> requires multidisciplinary applications of BIM. Therefore, the use of advanced technology is emerging in order to be able to respond properly to market challenges. BIM applications are moving towards IoT, safety, digitalization, smart building, social network analysis, and point cloud. Thus, automation will play a significant role either in providing a highly accurate 3D model for the existing buildings, or in providing a system that measures, collects, and analyzes data of the key performance metrics based on the IoT concept. Furthermore, a digitally empowered framework will enable the decentralization of facilities managemen<sup>t</sup> for single or multiple buildings [20,21], and could provide a finished product to end-users for cognitive building operation. In term of safety, professionals and researchers are working to develop an approach to integrate the risk factor in building an information model. The tool will be able to detect and quantify automatically any potential risk within the construction site and the life cycle of the project [17,19,26]. Several studies have applied social network analysis (SNA) to investigate major risks related to the act of building and to identify the network structure of all the contributor relationships [26]. Other research suggests using risk factors integration from an online application called the Safety in Design Risk Evaluator, which measures risks at the item-level in multistory buildings with a 4D building information model and a construction timetable [31]. Therefore, BIM trends as many other concepts are mainly heading towards the adoption of digital technologies, big data, IoT, smart models, and machine learning. The expertise areas extracted from the co-occurrence network include interoperability, IFC, lean construction, BIM implementation, energy e fficiency and BIM education. Most of these fields are technology based, which has led to a fast-growing knowledge of BIM and its sub-areas that we can see in the evolution pattern. Therefore, BIM education should be constantly upgraded to deliver a valuable knowledge of this dynamic platform.

BIM should be understood as cycle where are all the phases related to the building industry. These phases are: programming, conceptual design, analysis, documentation, fabrication, construction, construction logistics or management, operation and maintenance, demolition, and renovation. The clusters obtained in the previous section reflect almost all of these phases of the BIM, but the cluster of demolition and renovation are missing. This gap in BIM research is already pointed out by some recent works [76]. This shows that these two fields of research within the BIM; although they are currently not fully developed.
