I've received a beta account for [true knowledge] and decided to play with it a little. So far it's been interesting (although I can't say I've done much yet). Here is what I've done so far (I'm not adding any exact quotes here, just an idea)
My first question: "What is Earth's diameter?"
Answer: "Question understood, but the object that was recognized is not a circle: Earth, third planet in the solar system; Earth, the location of everything in this planet. Do you want to add a circle?"
Odd... Can't spheres have diameters? And yes, Earth is not a sphere, but people still have references to the diameter of the Earth. But, instead of trying to enter data on this debatable subject, I decided to simplify it:
"What is the diameter of a tennis ball?"
Answer: "There was an error processing the question."
"What is a tennis ball's diameter?"
Answer: "I don't understand what a tennis ball is, but it must be a circle or a sphere. Do you want to enter a tennis ball?"
I decided then to do it and it goes through asking you to write:
1) a short description of it to disambiguate the term for a human reader,
2) the plural of the term and the short description,
3) write synonyms of the term (I couldn't figure out synonyms for tennis ball),
4) A parent class (sphere? I tried ball, but they suggested sphere),
5) Questions of whether the "tennis ball" class is disjoint with other sphere children which I found quite interesting, but not as interesting as what came next
6) Is a sphere something intrinsic of an item, or something that an item can become and cease to be?
Very interesting set of questions. The sad thing is that when I finish all this, it forwards me back to my question and the answer is still the same: "I don't know what a tennis ball is". The classic UI problem of how to make users feel like they contributed with something by seeing what they did directly affect their experience, or clearly state that it might take some time to do so. Negative points here.
Anyway, I'll continue playing around and maybe I'll document more if I find something interesting. It's quite nice and disturbing the amount of projects out there hoping to leverage people to build structured data. Why can't they just collaborate with each other and specialize on answering the types of questions that they care about? Maybe they can even have different ways of you entering data, but it would be so much easier if they could just add this information to somewhere like freebase while they are at it!
Yes, I do feel guilty for choosing sides, so I'll add information about tennis balls in freebase too. The problem on freebase is that now I have to decide whether I call a tennis ball a ball and assume all balls are spheres (so have diameters) or consider a football a ball too and so there should be spheric balls and oblong/ovoid balls. ARGH!