Katy Perry isn't like Taylor Swift: when you listen to her upcoming album Prism, you won't have to wonder who she's singing about.  Katy's very open about revealing that several of the tracks concern her relationship with her current boyfriend John Mayer, including one about their breakup earlier this year.

Elle UK magazine reports that one of Katy's new songs, "It Takes Two," is about Katy's "acceptance that she played a large part in the split."  It was co-written by rising British star Emeli Sandé, who also co-wrote several songs on Alicia Keys' Girl on Fire album.  Another one, also about John, is called "Unconditional," and the magazine describes it as "an anthem of absolute love."

Katy tells the magazine, "I wrote it while we were still apart, and I just played it to him.  He was really moved."

John doesn't actually appear on Prism, but he's promoting it in his own way: he posted a photo to his Tumblr account of the gold-plated truck that Kat