Jonny Come Lately
The New Kid In Town
I believe it is loosely based on Orwell's Animal Farm. I've never actually read the book but from what I gather on Wikipedia it seems to be a one to one match with the characterizations of the animals.
I myself have never read Animal Farm, but I am familiar with the characters and ideas behind it. I can certainly see the similiarities with the album although I think there is a fundamental difference between the two as Animal Farm is a critique of Communism (most obviously in the Soviet Union) whereas Roger Waters was writing a critique of a western capitalist society.
The pigs in the book I believe are very similar to the three different pigs on Animals (in the sense that they have ultimate control), same for the sheep. However I think in the book the dogs are akin to a secret police force used to control the sheep, whereas on the album they are characterised as ruthless businessmen who have more power than the hapless sheep but are ultimately exploited by the pigs, though they don't realise this until it's too late.
One interesting thing about Dogs is that the verses sung by David Gilmour are lyrically brutal, while Roger's verses seem to show some sympathy for the dogs. When Roger seems to identify himself as a dog in Pigs On The Wing (Part 2) - see lines like 'any fool knows a dog needs home' - this clarifies what I think is a crucial difference between the dogs and pigs, with the dogs having to behave like they do to avoid the fate of the sheep, whereas the pigs are intrinsically 'bad' (they are outright and directly insulted, think 'bus stop rat bag', for instance, rather than criticised in general).