*2.1. Research Area*

The Sishengci historic district is located in Jinjiang District, Chengdu, China (Figure 1), and the district extends from Xinhua Boulevard and Yuefu Street in the north, to Shudu Avenue in the south, to Taisheng South Road and Hongxing Road in the west, and to Dongan North Road and Dongan South Road in the east (Figure 2). The Sishengci historic district is strategically located, with a deep historical and cultural heritage and many indigenous inhabitants. As a Chinese historical and cultural district, it still preserves the intact architectural style of the Republic of China era. The existing buildings are mainly western-style buildings and residential buildings with western Sichuan structures.

The Sishengci historic district basically follows the road structure of the traditional streets and alleys of Chengdu, forming a complete urban node as early as the Republic of China era. After going through the round-trip process of reconstruction, destruction, and reconstruction again in different eras, the district's buildings have also survived the construction characteristics of each period.

**Figure 2.** Sishengci historic district scope map.

#### *2.2. Space Syntax and Syntactic Variables*

Human perception of spatial systems is always dependent on small-scale space, and the integration of local information creates an understanding of the whole, according to the perspective of spatial perception. Therefore, understanding large-scale space begins with comprehending small-scale space. In spatial studies based on space syntax, it is presumable that the street network divides the large-scale urban spatial system into multiple identifiable small-scale core components. Axial lines analysis is the dividing technique that is most frequently employed. The dividing method that is most frequently used is axial lines analysis. In this study, we choose axial lines analysis, where the generated morphological variables are used by space syntax to quantitatively characterize the space, and axial maps are used to examine the spatial morphological structure [27]. The following section lists the main morphological variables.

#### 2.2.1. Connectivity

The number of spaces in the system that are connected to space *i* is indicated by the connectivity value [32]. In the map of the axial lines, transportation networks are abstracted as interconnected axial lines, which correlate spatial systems. The more an axial line is connected to other axial lines, the better the spatial accessibility and the higher the value of connectivity, as shown in the formula:

$$Con\_i = k \tag{1}$$

where *k* is the number of spaces that are connected to space *i*, *i* = 1, 2, 3, ... , *n*; *n* is the total number of spaces in the system; *Coni* is the connectivity value of space *i*.

#### 2.2.2. Control

The control value refers to the relative degree of control of space *i* over the spaces intersecting it [27], and the control value reveals the relationship between adjacent spaces in the system, as shown in the formula:

$$\text{Ctr}l\_i = \sum\_{j=1}^{k} \frac{1}{\text{Con}\_j} \tag{2}$$

where *Ctrli* is the control value of space *i*, space *j* is the space connected with space *i*, and *Conj* is the connectivity value of space *j*, *j* = 1, 2, 3, . . . , *k*.
