Wolfram Alpha suffers a bit from that, I think: You can query a great lot of things but for many of them it requires you to a) know about that you can query that, b) knowing <i>how</i> to query for that, c) how to give options, parameters. The natural language interface sounds great and makes for awesome demos (like »Wow, they can actually understand that?«), but it&#x27;s horrible for discoverability, especially in cases where you can try five different ways of saying the same thing but only the sixth would actually yield a result.