Right now, I'm reading Teofilo Ruiz' excellent book Spain's Centuries of Crisis, where he discusses how Aragon essentially ruled eastern Spain along with Valencia and Catalonia, while emphasizing the relative independence of the three states. In another book, perhaps by Ruiz, I read how Aragon, Valencia and Catalonia were essentially one political unit with each state having semi-autonomy.

So, how did this schema work? Did the king of Aragon rule over all three with Valencia and Catalonia having their own governments to worry about local matters? Were Catalonia and Valencia essentially independent? Did Aragon have any control outside of its immediate borders?