## 6 Authoring of BIM Structural Components Library  
### Design Principle Applied in Vernacular Architecture BIM Component  
Establishing precise design principles is essential to authoring accurate BIM models of VA components. According to [PERSON] and [PERSON] [26], dimensions such as length, height, roof slope, and purlin spacing in VVA, particularly in village communal houses, adhere to specific standards defined by the Sam Ruler. This system originates from the overall longitudinal length of the structure, termed \"Long Nha\" (denoted as \"L\"). This length is divided into one \"Khoang Thuong\" (denoted as \"L1\"), two \"Khoang Trung\" (denoted as \"L2\"), and two \"Khoang Thuan\" (denoted as \"L3\"), with each \"Khoang Trung\" and \"Khoang Thuan\" being equal in size. Figure 6 exemplifies this division: for a \"Long Nha\" length of L = 18a, the Khoang Thuong is L1 = 8a, each \"Khoang Trung\" is L2 = 5a, and each \"Khoang Thuan\" is L3 = 3a, where \"a\" represents the \"Khoang Ngang\" unit on the Sam Ruler. Column heights are calibrated to achieve a balance between aesthetics and structural integrity. The height of small columns (denoted as \"H\") ranges from 7b to 9b to avoid head collisions with the Veranda Roof. The height of the principal column (denoted as \"A\") is calculated as A = H + 8b, and the intermediate Column height (denoted as \"B\") as B = H + 3b, where \"b\" is the \"Khoang Dung\" unit on the Sam Ruler, typically maintaining a b/a ratio of approximately 2/3 [26]. Roof slope is determined by the b/a ratio, ranging from 55-60% for tiled roofs or 65-70% for thatched or palm-leaf roofs, with the \"Khoang Chay\" (denoted as \"c\"), representing the roof's diagonal length, computed using the Pythagorean theorem in a right triangle to ensure technical and aesthetic compatibility. Purlin spacing, which corresponds to the number of \"Khoang Ngang\", is determined by the \"a\" and \"b\" ratios, ensuring even distribution and optimal load-bearing support. Once designed and manufactured, these components are meticulously assembled to form a cohesive structural framework, ensuring precision and consistency. In actual construction, these frames are securely interconnected by horizontal beams, creating a robust system capable of efficiently distributing loads. The spacing between frames, known as \"gian\", is determined by the overall design and functional requirements. This term holds cultural significance in VVA, reflecting a rational spatial division tailored to the structure's intended purpose. Figure 7 illustrates a vernacular structure in Ho Chi Minh  
Figure 6: Example of design rules based on the Sam Ruler for a Communal Hall structure [26]. City, Vietnam [66], with five \"gian\", clarifying the concept. In this context, a \"gian\" denotes the interval between adjacent columns within the framework, forming an organized spatial unit. The choice of an odd number of \"gian\" (e.g., 3, 5, or 7) reflects cultural beliefs in luck and prosperity, aligning with traditional feng shui principles. These design principles underscore the pivotal role of the Sam Ruler system in VVA. Builders achieved a harmonious balance between aesthetic appeal and structural functionality by adhering to standardized proportions, such as Long Nha, Khoang Thuong, Khoang Trung, and Khoang Thuan, and calibrated column heights and roof slopes. These measurements, derived from Le and Cao, help faithfully recreate the characteristics of VA while optimally supporting the structure's load-bearing capacity and weight distribution. To effectively translate these traditional design tenets into an automated framework for subsequent application, several core principles will guide the process. Firstly, the foundational application of the [PERSON]'s proportional rules, as detailed Le and Cao [26], will be paramount to ensure dimensional fidelity in key aspects, like overall structure length (\"Long Nha\"), bay widths (\"Khoang Ngang\"), and roof geometries.