BOSTON — LIFE is full of contrasts for Queen Latifah.Say she wants to drive someplace. Most of the time it's easy enough. She gets in her car, a BMW 735i, and goes. But sometimes the police stop her, she says in an interview, for no other reason than to ask the question: What are you (you 21-year-old black woman) doing with the car? "What ... do you mean what am I doing with this car?" she says, acting out her response in these situations. "I earned this car - I paid for it in cash, in full." "I can't tell you how many times I've gotten stopped," she says. Then there's being asked to speak at Harvard University - twice, so far - where students study the rap she writes, and where she is introduced so deferentially that it embarrasses her. Queen Latifah's appeal to Harvard audiences is that she is the doyenne of the virtuous side of hip-hop and rap music. Her rhymes are almost entirely without descriptions of sex and violence, or snide, abusive putdowns. "I choose to stay positive, definitely, to do the right thing," she told a Harvard audience a year ago. And hearing Queen Latifah talk suggests that hip hop, for all of the hype, may be one of the few cohesive elements in American culture. Here's another bit of her Harvard talk: "This music is reaching different continents and is bringing people together - in America as well. "When you can get a 50 percent black audience, 20 percent Spanish and the rest white, together, to listen to music from a black artist - no fighting, a lot of partying, a lot of fun going on - and then to have the artist tell them some things to bring them even closer, to tell them they need not to be racist, they need to fight racism and things like that, to bring them closer without a fight, then we're making the world a better place." At 21, Queen Latifah is really too young to be the doyenne of anything, except that her 1989 album "All Hail the Queen" was greeted with such critical and popular acclaim that she was immediately dubbed the ruler of woman rappers. Her positive messages make her a good choice for mainstream journalists looking for a profile subject. Maybe her regal name helps, too. (Her real name is Dana Owens.) Now she's released her second album, "Nature of a Sista runs her own artist-management company, and is working on her acting career. She had a cameo role in Spike Lee's "Jungle Fever," and has appeared on "The Fresh Prince of Bel-Air hip hop's entry into primetime network television. She owns a video store in Jersey City, N.J., where she lives, practicing what she preaches about African-Americans investing in the community. Her BMW comes up in this new album, in a lyric that offers an example of why Latifah has a good reputation. "There are things I know about that I can say with the greatest of confidence," she says about her work. "They're really simple things that people can understand, like in a line in 'Bad as a Mutha' I say: 'Skeezer I'm not one. They're impressed by BMWs, huh? I got one.' "All that's saying is I'm not a cheap tramp who's going with a guy for his money or his car, so I can drive around in his car and think that I'm large [important] 'cause he's driving a Benz or whatever.... And there are a lot of girls out there who do that, and that's what I'm trying to change." In another song on "Nature of a Sista' " called "Fly Girl," Latifah describes what it's like to walk into a club: So I jump in the car and I go to the venue. Walk in the door now I'm on the menu. Guys in the house they're watching me, they're clocking me, there's no stopping me. Later in the song she tells them: Easy love is something that I ain't. Besides I don't know you from a can of paint. "Fly Girl" is clear, listener-friendly rap on a single designed for wide release. But some of Latifah's rap is there for the sake of the words and the rhyme. On one track she relies on the often-used form of exalting one's own talents over another rapper's: Feel the frost of my holocaust, I'm starin' at 'ya. Put in a bid on who will fall, I'm sure to match ya. Snatch your stature.... In spite of change-oriented lyrics, Latifah isn't necessarily convinced that fractious relations among races and sexes can be eased. For one thing, she has to endure the contrasts of her own life. One day she's standing behind a podium that says "Veritas" and the next she's too young and too black to be driving a too-nice car. "People need to stop sleeping," she says. In Latifah's view, hip-hop and rap music can awaken people by unifying them and by alerting them to problems. "Hip hop is not a music that you sit down and listen to and that's it," she says. "It gives you a lot of answers ... but it also gives you a lot of questions.... I don't think when you listen to [a hardcore rap] record, you just sit there and say, 'Yeah cops are all this and ... white people this and white people that.... You know, you start to ask yourself, 'Are cops everywhere like this?' or 'Are all the cops messed up?' and 'Are all white people prejudiced? To me, it prepares you for the world.... "You take R&B, you take pop [music], it's so beautiful, the lyrics are beautiful - love, love, love, love, love, you know? - which is beautiful, alright, because everybody loves love. But that's not what the world is all about. Everybody doesn't love everybody." "If we were just riding on a bus," she says to a white interviewer, "you wouldn't strike up a conversation with me, 'cause you don't know me.... But you don't have to know me when I'm making a record, because you're going to hear it ... and listen to the lyrics." Then she repeats: "You get to hear it. So we get to know each other. And you get to look at me ... and think about the things that go on in my community.... "You may have been sheltered [and] didn't realize people were racist. I mean white kids ... didn't even realize so many white people were racist.... They have been sheltered too, in a lot of ways, just like the black kids in the ghettos have been sheltered from dealing with white people. They don't know how to speak to them, just like you don't know how to speak to us. It's like the language barrier, slang vs. English." Latifah makes no apologies for hardcore rap, and doesn't reject it - it says things that must be said. And she dismisses critics who say that hardcore rap leads to violence or even suicide. "The kid that goes and kills hisself while playing [a] record is going to kill hisself anyway.... You want to go blame their problem on a [music] group, but the real truth was they really had a problem and maybe it was the fact that they felt nobody could understand it. You didn't make an effort as a parent, maybe, to connect with them.... "At this point," she adds, "parents need to realize it's too dangerous in our world for them to be parent and the child to be child - they have to be like brother and sister.... Me and my mother are like sisters in a lot of ways, and if it weren't for that fact, I think I would be just as screwed up as a lot of other girls out here. I probably would have had a kid already.... It was her letting me know that I could talk to her. It was her talking to me first and letting me know this. "See, this is the problem. [People] expect us to come and teach all of their kids. You understand? Like [hardcore rapper] Ice Cube was telling me: People expect, you know, [entertainers to create positive messages]. We're not responsible to teach their kids everything they're supposed to know to survive in this world, [parents are] supposed to teach them that. And that's why [they're] supposed to make a distinction between right and wrong, truth and false. You understand?... That's a parent's job, but we wind up teaching half the parents too."