Is the goal of this project to create one common database, which every organisation can use to display their subset of data, or do we want each organisation to expose their existing database via a common API, to simplify exchanging data?
I learned about In Common at the Vinicia Mapmakers meeting, and based on the (brief) discussion and with our own project in mind I had the idea that we were talking about the second thing, a network of databases. But after reading some of the discussions here I think In Common wants to create one shared database, similar to how OSM is one database, but you can tag the nodes and filter on these tags to get the views you want. The main goal then would be to share resources, and keep costs down so everyone can focus on their added value to the world instead of recreating geographical databases.
For Vicinia I think the network idea would be more interesting, because we want to enrich the data, adapt it to our models, and it would be a weird thing trying to fit all of that in a database that should be suitable to everyone. There a Linked Data approach would be more suitable (imagine we can link each Repair Café in our database to a canonical reference in another database!), but the problem with Linked Data is that it is cool, but doesn’t seem to have much traction outside the academic world.