# Exploring Data Model Relations in OpenStreetMap
## 5 Conclusions and Future Work
### Summary of Key Findings
The authors convert ways and relations into polygons without mentioning specific characteristics of the relations involved. The focus is on the tagsattached to the relations. With the available tags from relations, on OSM data from Germany, accurate LULC classes could be derived. * **Edit Frequency of Relations:** We calculate the Age of relations as the number of days between the date of download and the current date timestamp on the relation itself. In all cities, a large number of relations are edited within the last few years. Rome and Madrid shows different distribution of the Age of relations. We see that the vast majority of relation objects in all four cities have between 1 and 10 edit versions. Authors such as [PERSON] and [PERSON] [40] and [PERSON] et al. [8] have drawn attention to heavily edited objects in OSM with specific focus on those objects with high version numbers. For example those objects with version number greater or equal to 15. [PERSON] et al. [47] conclude from their global study of OSM that some maintenance actions, such as the addition of new tags to existing spatial objects, are much more frequent than other actions, such as the updating or the removal of existing tags. The distribution of version edit number towards lower version values on relations may indicate reluctance on the part of many contributors to edit relations within the OSM software. In their work on analysis of the history of OSM objects, [PERSON] and [PERSON] [49] find that over 90% of objects in the their analysis have three or fewer versions. However this requires further investigation in regards to relations. The complexity of relation objects may also have a significant role to play in their actual editing by contributors. [PERSON] et al. [50] argue that in the case of turn restrictions for navigation satellite imagery cannot testify to the existence of restrictions and contributing turning restrictions even for a single road to the OSM dataset may be extremely time-consuming. * **Relation Size:** The size of relations refers to the number of members contained within the relation itself. In this respect, relations are different to OSM nodes and ways which are single self-contained objects. In our review of related work, we were unable to find other reported results dealing with the size of relations in OSM. Subsequently, as a first step, we decided to investigate the general distribution of relation sizes within the four cities. Eighty per cent of relations in Madrid, Vienna and Rome have 10 members or fewer. Figure 2 visualizes the distribution of membership size when we consider only relations with 10 or fewer members as a sample of the entire population of relations for each city in Section 4.2.3. Super relations (those with more than 300 members do exist in all of the cities in small numbers). Considering a wider definition of super relations to include those objects with more than 100 members these only account for between 5% and 8% of all relations in the cities. We feel that the size of a relation may, in some way, be related to its spatial complexity. Anecdotally, we speculate that relations of small size will not be representing complex spatial relationships or topologies. However, relation size along would not indicate the true nature of the complexity of the relation. It would also be necessary to consider the members themselves within the relation. * **Contributors to Relations:** In the absence of a full analysis of the history of all edits to relations in each city it is difficult to draw robust conclusions about contribution patterns. However, it was observed that, in the current version of relations in the OSM database for the four cities, a small number of contributors are responsible for a considerable amount of the current version edits. At this stage of our work, it is difficult to accurately quantify the sociological factors most influencing the obtained results.