The second is actually a decent example of where the semantic web would probably fail because of the imprecision, but Google has succeeded to some degree. “When was grass invented” has no good answer because it’s a stupid question. You could interpret this as “when was grass discovered” but I suspect this is not the question being asked. Google has interpreted this as “when was the grass lawn invented”, which is probably what the user was actually asking. In both cases, the results are actually great (my first link was to the Wikipedia Lawn article).