Since a dog's life revolves so much around their owner (you're basically their whole life), there is a very good chance your dogs are dreaming about you. It's kind of heartwarming to think about.
Our golden retriever liked to lay his big head on my chest, his ear pressed against my heart, listen to my heartbeat and fall asleep. It always had the utmost happy look when it woke up again. Maybe it wanted to remember how it was like when it was still with its momma as a puppy.
Chasing rabbits.