# Literature Review of Digital Twins Applications in Construction Workforce Safety
## 7 Discussion
### Challenges and Future Works
#### 7.2.3 Information Processing  
DT, in the field of construction safety, allow users to understand the actual construction activities with the help of a digital replicate. Information processing is the main aspect of DT technology, which aims to solve how to identify and deal with hazards from synchronised construction activities. Adequate safety knowledge is necessary if an inspector wants to identify hazards. Similarly, for automatic identification of hazards, adequate machine-understandable safety knowledge is necessary for a VCS. Previous studies have tested automatic hazards identification for only a few dangerous situations. For complex construction sites with all kinds of hazard, the rule checking is inevitably slow, causing considerable delays. Therefore, it is necessary to optimise the rule checking algorithm, such as optimising the inspection sequence and skipping redundant inspection items. VCSs mostly use BIM as an information base to extract the required construction information or geometric models to achieve corresponding functions. However, for the massive amount of BIM information in a project, information retrieval and export consume large amounts of computing power [103]. In the steps of model transformation, information is lost [104]. These findings reveal that BIM's interoperability still has room for improvement.  
When recommendations to deal with the identified risks are proposed by a VCS, conflicts or new dangers may arise. For example, if there are two adjacent holes in the floor, the rule-checking system may recommend covering them with two separate planks, but the placement of the two planks would overlap, which is a conflict. Deeper logical relationships between rules should be studied to make the recommendations more robust. In future research, ontology should be developed to model the logical relationships between rules, describing in detail the relationships among workers, objects, and hazards, forming a digital knowledge network. The collected real-time construction activity information should be connected with the knowledge network from the perspective of semantics, which has the potential to improve the speed and accuracy of hazard identification. The application of ontology will also provide safety guidance for the application of new technologies in construction, including automatic driving [105] and 3D printing [106].  
To develop a knowledge network, rules, manuals, articles, and meetings are the primary means of sharing knowledge. However, in addition to the explicit knowledge that can be clearly expressed and effectively transferred, the sharing of tacit knowledge is crucial [107]. The tacit knowledge hidden in worker behaviour and construction data needs further research to be extracted. The retrospection and reflection on near-miss accidents can effectively avoid the occurrence of future injury accidents. Through a real-time tracking system [108] and heat map [109], near-miss accidents can be recorded in detail. Therefore, another potential research direction is to enhance the learning ability of VCSs, integrating knowledge acquired from near-miss accidents into the knowledge networks to extend the knowledge network.