I am afraid you are mistaken when you say that 'whose' only refers to people. 'Whose' is the relative possessive of both 'who' and 'which'. It can be used with inanimate objects too e.g.
'The house, whose roof was leaking badly, was in a dangerous condition.'
As to 'rules', many things that are presented to students as being 'rules' are merely pieces of advice as to how a structure or item is used most frequently. Some 'rules' are better than others in that they have few exceptions. However, a true rule has no exceptions and there are few of these.
Thank you for your proper correction. I have actually read this assertion concerning whose and which in the Michael Strumpf's "The Grammar Bible".I make it a matter of of principle never to pin o's faith on big authorities. You were in the right. Stimulated by your remark I inquired further in this subject.Really, whose is possessive form of who and which.It has sometimes been claimed that whose is properly possessive form of who and should be restricted to animate antecedent. But there is extensive literary precedent for the use of whose with inanimate antecedents. As in "The play, the style of which is rigidly formal, is typical of the period." and "The play, whose style is rigidly formal, is typical of the period."
But as this example demonstrates substituting of which may produce a stiled sentence.
Really there is a subtle difference between animate and inanimate objects.
Recently I have read the following Cronin's words: "Along the Terrace David went, his footfalls ringing and echoing amongst the other footfalls of the early frigid twilight. Dim shapes moved with him in comradeship, the shapes of the twilight men." Which of this substantive is animate or inanimate? The David hears greetings, brief but friendly. The miners' short "How, Davey" rings warmly in his ears - and he makes one "with the march of the twilight men."All these words expressing different aspects of united effort ("march", "massing forward in formation", "comradeship", "army") are there to delineate the state of David's mind-that of a class-conscious working man.
Thank you for the both, your keen mind and your sharply-pointed pencil.