Visualization Analysis of Research Hotspots and Frontiers of Flexible Space and Future Prospects

The proposal and delineation of flexible space is an effective approach to promote innovation in territorial management, improve the scientificity of spatial planning, and meet practical demands in the context of significant economic and social transformation. However, existing research focuses on preliminary theoretical exploration and case studies on individual cities/regions and is inadequate from the perspective of systematic and integrated research. We used visualization analysis software (CiteSpace5.6) to develop a knowledge graph of flexible space research based on more than 800 articles published between 1990 and 2020 on the topic of "Flexible Space" and "Flexible Planning", retrieved from two databases ("Web of Science" and "China National Knowledge Infrastructure"). The research drew the following conclusions: 1) The quantity of English literature had a significant upward trend, but the amount of Chinese literature increased first and then decreased. Most research focused on eco-environmental and engineering perspectives, and ecosystem services and land use suitability evaluation became the novel direction. 2) The cooperative network density of scientific research institutions related to flexible space research was 0.0042, indicating a relatively low degree of cooperation. The segmented cooperative network centered on several institutions including the Chinese Academy of Sciences and the University of Queensland in Australia, etc. 3) The most common knowledge groups included the concept and connotation of flexible space, flexible planning methods, and regulation measures. Features such as land reservation, mixed utilization, and space replacement were emphasized in the descriptive terms, while the use of spatial and quantitative analysis models for spatial optimization and evaluation of suitability were technical focuses,and the most widely adopted methods included decision support systems and agent-based models. Various regulation measures were proposed, with the "rigid-flexible combination" approach being amongst the most widely used. To promote theoretical and systematic research on flexible space, the theoretical framework should be built first as a general guide to related research. The theoretical basis and technical methodology should be improved with the support of multidisciplinary integration to enhance the scientificity and feasibility. Moreover, more case studies on various research areas should be carried out to improve the practicability.