## 3 Theoretical System Construction
### Application of Grounded Theory in Data Classification and Structure Construction
#### 3.2.2 Secondary Coding: Axial Coding Process  
After completing the open coding of the original data, the research entered the second stage of grounded theory - axial coding. This stage aims to integrate the categories, semantically summarize the large number of open concepts extracted previously, and construct a middle-level theoretical structure with relevance and explanatory power [24]. Axial coding is not a simple classification of keywords. However, based on concept saturation and semantic commonality, it identifies the \"category axis\" with a core connecting function, thereby supporting the generation of subsequent theoretical models. The research team finally summarised seven dominant middle-level categories through multiple rounds of comparison and analysis of the open coding results of 2638 keyword samples combined with AI semantic clustering assistance and manual annotation judgment. These seven dimensions are AS_application scope, CP_composition pattern, CYs_colour system, EL_element of Ornamentation, MT_media and craft, TC_theme context, and SM_meaning symbol. The summary results cover the typical elements of the phoenix pattern in terms of form, structure, colour, material, and symbolic meaning and reflect the accumulation and sedimentation of the phoenix pattern in historical evolution, media conversion, and contextual application; see Figure 5 for details. 1. Application scope dimension. In the \"application scope\" dimension, the study identified six typical application scenarios of phoenix patterns in social life, including the decoration of objects, clothing, and fabrics, architectural furnishings, religious rituals, cultural and creative graphics, and daily objects, as shown in Figure 6. Through the systematic induction of images and texts, the application of the migration and cultural function reconstruction of phoenix patterns across historical stages is presented. Among them, the object decoration category often includes precious items such as jade pendants and blue-and-white porcelain vases, reflecting the explicit expression of phoenix patterns in rituals and power systems. Clothing and fabric categories such as as traditional embroidery, traditional costumes, and auspicious court costumes emphasize the symbolic positioning of phoenix patterns in gender, identity, and hierarchical structures. Architectural furnishings include brick carvings, murals, door panels, and other components, reflecting the complex role of phoenix patterns as auxpicious amulets and visual main decorations in spatial structures. Religious ritual categories reflect the use of its image in the ritual evolution in Buddhist and Taoist culture; it is often seen on ceremonial objects, Shaolin Temple stone carvings, and sacrificial objects. In addition, the widespread regeneration of phoenix patterns in cultural and creative graphics reflects their translation from traditional contexts to modern consumer culture. They are often used in packaging, derivatives, and digital content, showing substantial visual simplification and communication adaptability. The daily utensil category incorporates the phoenix pattern into daily utensils and home decorations, strengthening its combination of practicality and beauty and completing the natural evolution of the symbol from \"de-hierarchy\" to folklore. 2. Compositional schema dimension. In the \"compositional schema\" dimension, the study systematically extracts and summarizes the typical styles and coding structures of phoenix pattern composition in spatial layout, visual organization and graphic evolution. Through a detailed analysis of sample images combined with the secondary coding process of grounded theory, six major composition types were finally established, which revolve around geometric structure, dynamic expression, element relationship, spatial hierarchy, aesthetic characteristics, etc. and constitute the core configuration modules in the graphic expression of phoenix patterns.