Relevance theory is a theory to study the law of "linear" relationship between the constituent elements in urban material environment, which is called correlation coupling analysis. These "lines" can be traffic lines, linear public spaces and sight lines, such as various traffic arteries, pedestrian walkways, sequential spaces, etc. Sightseeing corridor and landscape axis. Through the analysis of these "connecting lines", we can dig out the rules of formal combination and the motivation of morphological elements, with the aim of organizing a related system or network, so as to establish a comprehensive structure of spatial order. The establishment of correlation and coupling order can be divided into two levels, namely, material level and internal motivation level. From the internal motivation, it is usually not only the connecting line itself, but also the internal organizational functions of various "flows" on the line, such as people flow, car flow, logistics, energy flow, information flow, etc., which connect the spatial elements into a whole.
The connection theory provides the guiding ideology for the establishment of urban spatial order. It puts the importance of "relationship" and "association" at the top of the urban spatial structure, which not only provides a theoretical framework and analytical principles for understanding the organization of urban spatial structure, but also provides ideas and means for restoring, excavating and creating a harmonious and unified space on this basis and realizing the organic unity of the new structure with the original structure, internal structure and external structure.
Both the theory of relationship between figure and ground and the theory of connection aim to explore the relationship between urban spatial morphological elements and related structural organization. Transik divides them into three relationships, namely, morphological relationship (figure-background analysis), topological relationship (correlation coupling) and type relationship (place theory). It can be said that the clear organization and establishment of these three relationships in structure is the basis and prerequisite for establishing a certain spatial order and corresponding visual order.