## 3 BIM and DTs--Latest Development Trends and Challenges
### Implementation of IoT Paradigm and Data-Based Solutions  
The basis for each of the aforementioned solutions is data, resulting from both design assumptions and standard requirements, as well as operational data. This includes information on the operating status of building infrastructure subsystems, the intensity of the utilization of rooms, and the environmental conditions prevailing there. Moreover, there have been significant changes in the manner in which these data are acquired and processed for the purpose of utilizing BIM and DT models in the context of building applications. Now, instead of relying solely on BIM data, engineers and integrators combine them with information from fully distributed IoT sensors, monitoring systems, and other sources. This results in a more comprehensive DT that more accurately reflects the real object and is directly related to BACS and BMS functions. The trend is to enrich the DT with data from different sources (BACS sensors and actuators, smart meters, etc. ), allowing for better modeling and analysis of reality and facilities as a whole [23; 76; 77; 78]. Furthermore, instead of relying just on traditional methods (periodic monitoring, measurements), with DTs, engineers are able to create realistic simulations. These virtual experiments predict the future functioning of a building, thereby optimizing its performance in a multitude ways. In addition, they enable testing of new technologies, such as photovoltaic panels or intelligent energy management systems, in a secure virtual environment [47; 79; 80]. Moreover, these virtual copies of buildings can not only simulate how they work but also assess the impact on the environment. Engineers can test different building materials, heating systems, or ventilation solutions in the DT to choose the most environmentally friendly ones. In this way, DTs make it possible to design energy-efficient buildings that use less water and emit less pollution [25; 79; 81]. Making full use of the potential of BIM and DTs in the construction industry faces a number of technological and organizational challenges. In [52], [PERSON] et al. discuss three main data quality factors, completeness, complexity, and flexibility, in the context of organizing advanced BIM for various BACS open standards: KNX [82], LonWorks [83], and BACnet [84]. Bearing in mind all elements of BACS standardization like communication media with network topology, network variables, and data objects, as well as functional profiles with logical bindings, the authors analyzed usefulness of the BIM concept in advanced BACS and BMS platform design and integration. Additionally, the paper [30] provides a list of the most important research trends/challenges for BIM developments in the context of BACS design and integration support. These include the following: (i) the establishment of an open platform for the integration of multiple BACS and smart building technologies, (ii) the multidimensional consideration of BIM software standards, and (iii) data format interoperability with universal data tagging. Considering these trends, it should be noted that in the area of automation, the lack of system integration, the variety of data formats, and the shortage of qualified staff with the right knowledge and skills represent the most significant obstacles to be overcome in the field of automation. Project challenges are focused on the problems of data exchange between BIM/DT platforms, the lack of seamless data transition between project stages (from design to operation), and the need to optimize the level of detail of models according to the specificity of the stage. Optimizing organizational structures for efficient BIM/DT use is also a key aspect, according to [23]. Once these challenges have been overcome, BIM and DTs have the potential to become powerful tools that can significantly increase the efficiency of construction projects, reduce costs, minimize errors, and improve the overall profitability of projects.