Abstract
The need to act on urban expansion has been a common concern throughout the history of urbanism. Different authors have shown how in industrialized countries the old distinctions between urban and rural become blurred. The location and conformation of new leisure, commercial and tertiary objects have become triggers for new looks at the urbanization edges of industrial cities. Although they have been less explored in non-industrial cities or cities with a lower degree of industrialization, different studies show that these characteristics seem to be combined there with other factors such as social housing, progressive expansion of the urban fabric and degraded areas. Nevertheless, could there be a theory that enlightens the conditions and transformations of the metropolitan edge and guides their research? The aim of this work is to compare four key approaches: spaces in socio-spatial transformation, multi-actor project, multiple, dynamic and heterogeneous uses, and non-universal spatial delimitation, focusing on three categories: concept, attribute, and methodology. This research is grounded in the selection of relevant publications based on their substantive scope, significant impact factor index, and/or number of citations, as well as the international recognition of researchers. These findings underscore the importance of theorizing the metropolitan edge as a process that transforms inherited spaces according to their socio-economic, historical, and environmental contexts. The results reflect the need for denominations and classifications that help us to differentiate analytically and cartographically the multiple landscapes of the metropolitan edge and question us about the specificity of this territory that extends between urban nuclei and rural space, the processes that have overlapped over time, and their logics.