The problem these things have for me is managing the hierarchy. My entry for "NSMutableArray", does that sit under "Data Structures", or "Objective-C" or "Cocoa

The problem these things have for me is managing the hierarchy. My entry for "NSMutableArray", does that sit under "Data Structures", or "Objective-C" or "Cocoa"? I can see that I'd want to make my way to it from all three trains of thought.