Dawn of war and Warhammer

[eLdavis]

I have heard a lot about Warhammer, especially since the news came out that Henry Cavill would be working on a Warhammer project. This has made some none RTS gamers carry out research on Warhammer. Is dawn of war related to Warhammer? I have come across some persons who say dawn of war is sequel, while there are others who say dawn of war is just based on Warhammer but a different game on it's own.