The osm2pgsql code contains a part called the “middle”. The middle is responsible for keeping track of all OSM objects read from the input file(s), their attributes, tags, and, most importantly, the relations between those objects. This is needed for several reasons.

Back in September we launched the new osm2pgsql.org website. At that time it was still quite rudimentary. Over the last months a big part of my work for the OSM Foundation was to work on that site.