# An Indoor Space Model of Building Considering Multi-Type Segmentation
## 2 Conceptual Framework of Multi-Level Indoor Space Model
### Semantic Framework of Multi-Level Indoor Space
The room space is enclosed by the top surface, the ground, and the wall. The presence or absence of top surface shielding (such as the roof) is considered to be the main sign distinguishing the indoor space and outdoor space of the building (Figure 5). In this kind of closed building interior space, in order to meet the requirements of the private living environment, the internal closed rooms satisfying different functions are further defined [36]. Room space is the basic unit that constitutes a building. In the process of architectural design, the building components divide the indoor space for the first time to form a group of room spaces. The function of space is often used as the classification basis, and the single room space is divided into four categories: equipment space, connecting space, control, and management space, and use space. Due to the lack of vertical segmentation of the floor slab, an indoor space spanning multiple floors is formed in the building, that is, a cross-floor space. As the internal structure of buildings gradually becomes more complex, cross-floor spaces are becoming more and more common. If only relying on the classification method of space function, the cross-floor and segmentation characteristics of indoor space will be ignored. Therefore, this article will classify the room space in a combination of space segmentation features and functions. According to whether the room space has the characteristics of spanning multiple floors, first divide the indoor space into single-floor space, split-level space, and cross-floor space, as shown in Figure 6. Then, it is divided into closed space and semi-closed space according to the division degree of the boundary members of the single-floor space. The semi-enclosed space is divided into balconies, canopies, pavilions, etc. according to the use function, and the enclosed space is divided into indoor spaces such as ordinary corridors, offices, bedrooms, kitchens, and living rooms according to different functions. The split-level space is formed by the different floor heights of the same indoor space. This type of space is a special case of the indoor single-floor space. Depending on whether the space contains transitional components such as stairs and ramps, the split-level  
Figure 5: The distinction between indoor and outdoor spaces based on the top surface. space can be divided into sudden changes in split-level space and gradual transition spaces. The cross-floor space is divided into air duct wells, flue wells, elevator shafts, duct wells, atriums, halls, and other spaces according to different functions. (5) Functional subspace  
A functional subspace is the indoor functional area formed by dividing a single room space by indoor components such as screens and furniture. The lowest-level space in the indoor scene no longer includes the lower-level space. On the basis of the semantics of indoor space, according to the characteristics of indoor space segmentation, this paper continues to analyze the semantic hierarchy of single room space in more detail. As shown in Figure 7, according to different aesthetic and functional requirements, the space occupied by interior components will be subdivided into a single room space and divided into a group of sub-spaces with different functions. The room space is composed of several indoor functional subspaces, which are divided into interface subspace, free navigation subspace, and activity functional subspace (Figure 8). The interface subspace is the space occupied by the interface entities in the indoor space, which mainly includes the top surface subspace, the wall subspace, and the ground subspace (Figure 7a). The free navigation space is a free space used for indoor navigation and wayfinding, which does not contain indoor component entities. The activity functional subspace is a regional space that satisfies people's indoor leisure, office, entertainment, and other activities, usually including indoor furniture, home appliances, and other activities-related component facilities.