I remember the first time I read that "wessen" was the genitive of "wer." The next day, in my German class, I said something like "Wessen ist diese Kuli?", and got a verbal slap on the wrist from my teacher. Why, then, is this classified as a "genitive", when it is acting much more like a possessive? The reason I'm asking about this is that I'm writing something where I say that "whose" is an example of case in English, but then I was not so sure about it and decided to ask the Germans, since cases are more or less extinct in English. The equivalent of "wessen" in Russian is "чей", which, to my knowledge, is not classified as the genitive of "кто".