Resumen
The OpenStreetMap (OSM) geographic data model has three principal object types: nodes (points), ways (polygons and polylines), and relations (logical grouping of all three object types to express real-world geographical relationships). While there has been very significant analysis of OSM over the past decade or so, very little research attention has been given to OSM relations. In this paper, we provide an exploratory overview of relations in OSM for four European cities. In this exploration, we undertake analysis of relations to assess their complexity, composition and flexibility within the OSM data model. We show that some of the patterns discovered by researchers related to OSM nodes and ways also exist in relations. We find some other interesting aspects of relations which we believe can act as a catalyst for a more sustained future research effort on relations in OSM. These aspects include: the potential influence of bulk imports of geographical data to OSM, tagging of relations, and contribution patterns of edits to OSM relations.