Dogs in dreams usually stand in for loyalty and the people, or parts of yourself, that feel dependable and protective. A friendly dog can reflect trust you're building or already rely on, while an aggressive or wounded dog often points to a bond that feels strained or a loyalty you're questioning. Either way, the dream is asking who, or what in you, is meant to guard and be guarded.
Knowledge is a process of piling up facts; wisdom lies in their simplification. (Martin Fischer)