One of the great things about the combination of maps, geo, location and London is that roughly once a month there's some kind of meetup happening in the city on these themes. One of the longer running players in this space is the Geospatial Specialist Group of the British Computer Society which is being relaunched and reinvigorated as the Location Information SG. Earlier this week I gave a talk, but what to talk about?

It didn't take too long to come up with a suitable theme. In my current day job, consulting with open data specialists Lokku, I come across the benefits and the challenges in using open data on almost a daily basis. One of the earliest lessons is that nothing is simple and nothing is straightforwards when you bring licensing into a field and open data is no exception.

Although I can't find the originator of the saying that there's no delete button for the internet, it's a saying that's very true. If you put something up on a web site, be it a photo, some text or perhaps a file of geographic data there's a very good chance that someone else has a copy, even if you subsequently take the original down. It's a sort of digital whack-a-mole.

This is all too apparent in the story of Yahoo's GeoPlanet Data download. When I was part of the Yahoo! Geo Technologies team, we released a public download of the Yahoo! WOEID data set, under the CC BY 3.0 license, in 2009 at Where 2.0. More about that license in a moment.

As Yahoo! continues to undergo change under the leadership of Marissa Meyer, the current data file and all earlier versions were taken offline. Visit the GeoPlanet Data page on Yahoo's Developer Network site and instead of a set of download links, you see "We are currently making the data non-downloadable while we determine a better way to surface the data as a part of the service.".