Author: lars[at]aronsson.se
[Added to the original trac issue at 11.58pm, Thursday, 9th February 2006]

An area is a sequence (a snake) of line segments that bites its own tail. A snake that doesn't bite its tail is a line train, a.k.a. a "street segment". Street segments end at intersections, which are points that are somewhat more important than points in the middle of a snake. In an export format such as the ESRI Shapefile, intersection points must have identifiers but points in a street segment don't need to.

These higher level objects (street segments, areas) should have attributes, e.g. street names, traffic types, vegetation types, that would apply to every member line segment or the entire area enclosed. But individual line segments should not have attributes. Initially, all previous line segments could be converted to street segments of their own, each consisting of a single line segment, but then OSM would benefit from joining street segments into longer runs of line segments. This could be done automatically as long as two connected line segments have the same set of attributes, e.g. none at all.

For areas, no line segments should cross, but this could be the case for street segments, for example for a motorway exit that turns and forms a bridge over itself before it joins another street segment.