2012/9/24 Jochen Topf <[email protected]>: > http://blog.jochentopf.com/2012-09-23-multiple-layers-for-osm.html > If anybody wants to comment, I think this mailing list is the right place.
IMHO there are different requirements for these layers according to what is on them and how it is related to the data on other layers. E.g. the birds routes would not create much problems because they are only roughly linked to current OSM-data, while for the historic data layer I think it would be desirable to have that directly linked (or at least a possibility to link it) to the current data. This is important when there are remains of the historic objects that are still (also partly) present in the current world. These could be either physical but also "conceptual" (e.g. parcels of a roman castrum which are still valid for todays town, leading the streets (=voids) to be where they used to be). Other examples for this might be city walls, ruins and other remains of historic buildings, historic walls, ...). The problem here is not with static data but arises from the fact that our current OSM data is in continuous motion: as soon as someone moves the current city wall (or refines it) in order to improve it, the historic-layer city-walls should also be refined (or they will get out of sync). We could maybe have something like hardlinks on filesystems for OSM-objects (nodes/way/relations) to solve this? In other cases it might not be desirable that historic objects change when the current objects get modified (i.e. this will also raise complexity a lot for the mapper, as he will have to decide for his edits whether they should also be applied to linked data, which is likely "specialist data"). Another similar concern I have with layers is that of fragmentation of the data which currently is all in the one main layer. In the past there were some people asking for separate thematic layers like landuse (e.g. in order to not show them in their editor), and introducing a layer-system might likely lead to fullfilling this desire. I see this as a problem because landuse is strongly tied to other objects like streets, building lots, and other polygons (e.g. amenity, leisure, place-polygons) and moving or editing only part of this data will also lead to out-of-sync-geometry between layers (won't fit one over the other). To avoid this people would have to look at all layers, which in the end eliminates the benefits of separate layers. cheers, Martin _______________________________________________ talk mailing list [email protected] http://lists.openstreetmap.org/listinfo/talk
