Freebase is by far the most flexible database I have heard of. It is a very cool concept indeed, and it allows amazing discoveries. It also provides a free sevice for querying and inserting data.
Freebase schema is this: Domain, Type, and property. That’s it. And with this little schema you can have everything, absoloutly everything. Ofcouse flexibility comes with a big price tag on cost of managing stuff that we take for granted in our rdbmses. For example assurance of the integrity of data sounds to be very challenging. This doesnt make freebase style the scema of choice for enterprise, but wait a minte! Really interprises can not benefit from such database? Sure they can and I argue it is a necessity for any big enterprise.
I keep it short for today and will revisit the topic later.