[photochemsyn]

Thanks! I read the article, I read the post the article is responding to, I read all the comments and still I had no real idea what it all was about until I read your comment.

It could be an example of an author assuming a general audience already knows the insider information but then I don't know who the target audience really was. This is the kind of thing that probably should have been spelled out in the introduction, with a link to something like this:

https://labs.mapbox.com/mapping/osm-data-model/