One of the things I like to do when on holiday is spending huge amounts of time and money in book shops and then more time reading the books. And inevitably the time runs out faster than the books, so my stack of unread books keeps growing. I recently added a new bookshelf conventiently located near my bed just for the unread books. There are just too many interesting things and interesting books about those things out there…

The OpenStreetMap project gets bigger every day. More people edit the data which leads to more data in the database and this to more people using the data. And with the growing database it gets harder and harder to see whats in there. Gone are the days when the common mapper would need to know maybe a dozen different tag keys, each with just a handful of typical values. Today people tag parking spaces and public transport, power lines and penguin pools in their local zoo. Some people are valiantly trying to keep up by documenting tags in the wiki, but sometimes that seems to be a lost cause. There are only about 550 wiki pages describing a key, but there are about 20,000 different keys in the database (about one third only used once, many will by typos) not to mention the 50 Million different tags. What are all these tags? How are they used and by whom? The endless discussions on the mailing lists about what tags to use are partly because the world is complex and fitting everything in our tagging model is not easy, but they are also in part a symptom of this confusing situation.