# A Typology Model of Temporary Facility Constraints for Automated Construction Site Layout Planning
## 4 A Constraint Typology Model for CSLP  
This section presents a constraint typology model that CSLP automation models can use for construction site layout optimization or validation of the created construction site layout (Figure 3). The proposed model includes the definition of six constraint types and seven subtypes, which characterize 42 constraint instances identified in 11 temporary facilities. Three constraint types (i.e., dimensional, regional, and relocation) concern a single object laid out alone, and the other three constraint types (i.e., non-overlap, inter-facility distance, and visibility) concern about relationships between multiple objects placed.  
In order for CSLP automation models to derive practical results, it should be possible to create a construction site layout that complies with constraints during the optimization process. To do this, all constraints must be represented in a computer-interpretable form so that the CSLP automation models can examine the compliance with the constraints. The site space for laying out temporary facilities in CSLP automation models is generally composed of grid cells for the purpose of reducing the search space. The shape of the object is also often represented as a rectangle to simplify the calculation process. In general, one grid cell is the smallest region occupied by the object, and as the cell size decreases, the calculation time increases while the accuracy increases. The size of the cell can be adjusted according to the size of the site and temporary facilities as well as the accuracy sought by the planner [31, 41]. Accordingly, in this study, the site is represented as a two-dimensional grid with an \((x,\,y)\) coordinate system, and the origin is established at the lower  
Figure 3: CSLP constraints types and subtypes.  
left corner of the area. The temporary facility \(i\), represented as a rectangle, is expressed as the lower left corner of \(i(LLC_{i})\) (i.e., \((x_{li},y_{li})\)) and the upper-right corner of \(i(URC_{i})\) (i.e., \((x_{ri},y_{ri})\)) according to [PERSON] and [PERSON] [34] (Figure 4).  
Meanwhile, the proposed typology model was supplemented according to the opinions of experts during the validation process. The opinions were categorized into five types as shown in Table 2. Then, opinions that required detailed modification of the constraints (CT1) (e.g., \"The radius of T/C should be dealt along with the tip load.\") and comments on the choice of words or typos (CT2) (e.g., \"It should be clearly determined whether the gate is for a vehicle or for a pedestrian.\") were reflected in the creation of this model. However, opinions the authors disagree with for a valid reason (CT3) (e.g., one expert gave a negative opinion on the necessity of a constraint, but other experts agree that the constraint is necessary), comments that do not fit the context or have already been reflected (CT4), and opinions whose meaning was not clear (CT5) were not reflected. Through this process, 33 comments (42%) out of 78 were finally reflected in the creation of the constraint typology model.  
\begin{table}
\begin{tabular}{c c c c c} \hline
**Comment** & \multicolumn{2}{c}{**Number of**} & \multicolumn{2}{c}{**\% of**} & \multicolumn{1}{c}{**Model**} \\
**Type Code** & **Comment Type Description** & **Comments** & **Total** & **Modified** \\ \hline CT1 & Substantive comment that required modification has & 23 & 29\% & Yes \\  & been provided & & & \\ CT2 & Typo, format error, or word choice issue & 10 & 13\% & Yes \\ CT3 & Authors disagreed with the comment for a valid reason & 6 & 8\% & No \\  & Comment is out of context or has already been & 35 & 45\% & No \\ CT4 & reflected in the context. & 4 & 5\% & No \\ CT5 & Meaning of comment was not clear & 78 & 100\% & - \\ Total & & & & \\ \hline \end{tabular}
\end{table}
Table 2: Comments on constraints typology model and author responses.  
Figure 4: Representation of grid cells and temporary facilities on site.