# Knowledge Management in Construction Health and Safety Based on Ontology Modeling
## 1 Introduction  
Due to several general characteristics of the construction process, including lengthy construction times, distinctive site conditions, multifaceted construction technology and heavy reliance on the environment [1], construction is regarded as one of the most unsafe industries worldwide [2]. Construction accidents on building sites usually lead to casualties and property loss. For this reason, researchers and stakeholders are increasingly focused on health and safety (H&S) management during all stages of the project lifecycle.  
In this context, construction H&S management has long been a subject of intense discussion. Typically, H&S information and knowledge are gathered from a range of sources, primarily in unstructured formats. They include expert experience, construction drawings and organization plans, risk case bases and other documents from projects [3]. However, the maintenance of this knowledge has not been sufficiently formalized so far, and this disorganization hampers stakeholders from taking effective H&S management in the following ways:  
1. It is unlikely that enough H&S knowledge can be possessed to cover all eventualities during each construction phase. For instance, designers may overlook specific design safety knowledge necessary for the project's success; weak H&S management could be blamed for oversights such as this. Similarly, during the construction phase, risk managers can make bad decisions, particularly if they are new to the role.
2. To support H&S management on a project, the diverse groups involved, which include general contractors and subcontractors, generally design separate knowledge systems that function as support resources for decision making [4]. However, the knowledge required for H&S management is usually stored in unstructured forms and represented in different data formats in these information systems [5]. Therefore, the same object set could be defined in various hierarchical classifications, with thesame concepts expressed by a different party. As a result, the risk reports output of the same project from these systems could be expressed in various forms and without a unified standard.
3. Establishing enhanced H&S management can be accomplished by (i) sharing all relevant information, including the scope and type of project, method of construction, procedures for safety management and onsite data conditions and climate; and (ii) communicating such information across diverse groups and projects. For example, during the construction process, risk managers may require risk information from other sections (and even some data from other projects) to serve as a reference when making decisions. However, the exchange of information among different project sectors is inefficient based on current knowledge systems.  
The abovementioned factors trigger concerns about the standardization and formalization of H&S to the demands of highly efficient and effective decision-making for H&S management. Some argue that the development of a unified knowledge model both philosophically and linguistically facilitates H&S knowledge representations; however, this pertains not just to data or hypertext, but to whether this information is exchanged in a machine-interpretable manner. Ontology is clearly defined as a shared concept [6]. Ontology technology has presented knowledge in a structured way by classifying objects and their properties and the analytical correlations between them within a particular domain, thereby enabling information to be amalgamated, accessed and reused [7]. It can facilitate person-to-person communication. Furthermore, it can provide a way to capture and translate human knowledge into a machine-readable environment, which promotes human-computer interactions [8].  
In the end, the proposed HSM-Onto becomes a platform for the standardization and formalization of a domain knowledge model of H&S management, which focuses on explicit specification, semantic attributes and unified H&S knowledge.