Context really matters. One of ours used to lip-lick out of excitement when waiting to be taken for a walk.
My older one sometimes appears aggressive to other dog owners when she jumps forward and tells off, with 2 or 3 sharp barks, a rude young male who has just roared up to her and shoved his nose in her face, totally ignoring all her 'back off, buster' signals. The younger dog will pull back, ears and shoulders lowered. Mine will then stand there, head up and tail stiff. The other dog at this point will usually come up to her submissively, they will exchange a polite greeting, their body language will totally relax, and it's over. Any query from the other owner and I just say, She's within her rights to not like being rushed.
I've seen a few videos where canine communication is broken down and they're fascinating.