## 3 A Construction Information Classification System for Construction Lifecycle Information
### Unit Works Defined by Construction Objects and Activities  
Road construction projects encompass various works during the design and construction phases. Notably, the specifications of the target facility may undergo changes, and the content of activities can change throughout the construction lifecycle owing to advancements in engineering technology, the development of new construction methods, and fluctuations in social conditions. Therefore, effectively managing construction information involves maintaining continuity between stages, ensuring that the changes occurring in each stage are recorded and traced back to the preceding stages.  
In cases where construction plans are modified, the hierarchical structure of the construction objects enables the easy selection and modification of objects that need revision. Simultaneously, associated activities can be modified concurrently or at a later stage. During the execution of the unit work, activities can be assigned or newly specified.  
As shown in Figure 7, we generated unique identifiers for the construction objects, using a hierarchical classification system. Similarly, activities within the faceted classification areas also received unique identifiers based on their hierarchical classification. These identifiers were then employed to associate and digitize the pertinent information. In road construction projects, a unit work can be represented as a combination of these unique identifiers for construction objects and activities. To achieve this, we formulated a  
\begin{table}
\begin{tabular}{c c} \hline
**Activity** & **Definition** \\ \hline Billable & An activity responsible for changing the state of the target product (e.g., construction, modification, maintenance, and demolition), and determines its unit cost. \\ Grouped billable & A group of similar billable activities associated with a specific target product and collectively influenced by the condition of that product. \\ Elementary & A unitary activity constitutes a billable activity, and it may necessitate quality assurance and safety enforcement. \\ Intangible & An activity that cannot be directly tracked from the target product’s state but is still billable. Safety enforcement activities serve as an example. \\ \hline \end{tabular}
\end{table}
Table 2: Types of activities.  
unique identifier for a unit work, referred to as a JOB, by combining the respective unique identifiers using Equation (1), allowing for the seamless linkage of relevant information.  
\[\text{JOB}(id_{JOB})=\textit{Construction Object}(id_{co})+\textit{Activity}(id_{ ac}) \tag{1}\]  
When changes occur in either the construction object or the activity of the JOB, a unique identifier is generated using Equation (1), combining the relevant information. This approach involves defining the construction object and activity individually and combining them as required according to the multi-story expandable systematic hierarchical (MESH) system.  
The generated JOB inherits information from the construction object and activity without requiring any separate attribute information. Managing the construction object and activity information separately and applying the MESH system significantly enhanced the flexibility of the road construction information.