Madeline says Hello

Last week we were taking care of a friends dog, Barney. When we brought Barney home and introduced him to our dogs, they said hello to each other in the usual dog way, sniffing each other's bottoms. Madeline, very curious about this asked, "what are they doing"? I told her they were saying "hi" to each other and that, that is one way dogs say hi. Madeline said ok, laughed and went on her way. A few hours later I notice Madeline with her hands on her knees and legs bent with her bottom in Barney's nose. I asked her what she was doing and her reply..."I'm saying hi to Barney"!