## 5 Discussion
### State-Of-The-Art Industry 4.0 in the Construction Industry
BIM (within the planning domain), as the center of construction digitization together with Industry 4.0 (production domain), is able to close the digital gap that still exists and sustain the impact on future building processes [59]. The innovation in and approaches to construction automation are still in their infancy [62] and not fully employed as the technical aspects of the available technologies are still being investigated though some technologies have reached maturity, such as BIM, cloud computing, mobile computing, and modularization [32]. The fact that construction projects are becoming increasingly complex despite construction being a flat market for the previous five decades requires Industry 4.0 as a solution for a new business model [24; 25]. This has occurred because, currently, the construction industry has one of the lowest capital investments as well as low capital intensity [25] with the lowest R&D intensity [32] compared to other sectors despite being a major contributor to the employment and economy of many countries [63]. The fragmented supply chain of the construction industry, which includes several small- and medium-sized enterprises (SMEs), limits the ability to invest in innovative technologies [33]. Another reason behind the slow adoption is because the gap between construction and manufacturing is relatively huge though both industries are categorized into the same group and work together [24]. The unavailability of a dedicated process change strategy, dedicated implementation plan, and business strategy alignment have also contributed to the slow adoption. Since Industry 4.0 creates value that transforms the overall business strategy in the construction industry, there is a need to propose some strategies for implementation. With the capability to automate both design and manufacturing processes and the possibility of handling a heterogeneous and significant amount of information, Industry 4.0 is expected to be able to improve the quality and productivity of construction and attract domestic and foreign investors. This review, though we are not claiming it to be exhaustive, has provided an overview of Industry 4.0 concept in construction industry in the last five years. The selected papers revealed the active collaboration between BIM with technologies from Industry 4.0 (Figure 7), such as the use of BIM to support design decisions for mass customization production [54], structural health monitoring (SHM) using open BIM [43], allowing schedule monitoring in real time [50], smart steel bridge construction enabled by BIM and IoT [51], and a digital platform that uses augmented reality (AR) combined with BIM to provide workers with relevant information in real-time [58]. However, the pattern of topics discussed are broad and conceptual. The targeted papers only mention the benefit of Industry 4.0 to the construction industry conceptually. A detailed study should be completed to understand the benefits brought by Industry 4.0 to the construction industry. In addition, studies are lacking on management processes for overall project life cycle as well as the operation, and tactical and strategic planning in this collaborative and autonomous synchronization system. Studies in this area are needed in order to transform the construction network and construction economy and to integrate BIM with Industry 4.0 technology. The relationship of Industry 4.0 as the production domain with BIM as the planning domain acts as the core structure of the cyber-planning-physical system, influenced by the benefits and challenges of Industry 4.0 for the construction industry is illustrated in Figure 8[32; 59; 64]. Figure 7 shows how the physical and cyber domains are controlled by the planning domain. The bi-directional coordination between the physical domain and cyber domain has the potential to improve real-time progress monitoring and control the construction process, track changes, model updates, and exchange information between the design and operational stages [65].