This year’s Rock and Roll Hall of Fame induction class isn’t short on variety – and that’s the way the Rock Hall likes it. From new-school artists with a touch of hip-hop (The Beastie Boys, Red Hot Chili Peppers) to rockers with 1960s roots (Small Faces/Faces, Donovan) and, of course, Guns N’ Roses, the induction class of 2012 is bigger and broader than ever.

But rock purists have taken issue with the induction of acts they view as existing outside rock’n'roll, whether it be pop acts like ABBA (class of 2010) and Madonna (class of 2008) or hip-hop artists like Run-DMC (class of 2009). In gearing up for Saturday’s 27th annual Rock Hall induction ceremony, CBS Local spoke with the Cleveland-based music institution’s Jim Henke, Vice President of Exhibitions and Curatorial Affairs, about how the museum and its staff define “rock’n'roll.”

In our conversation, Henke cites the wisdom of Public Enemy rapper Chuck D, a friend of the Rock Hall who came out when the museum opened the first-ever major museum exhibit dedicated to hip-hop, “Roots, Rhymes and Rage: The Hip-Hop Story.” (That was in 1999, and D will return Saturday to help induct the Beastie Boys.) As Henke recounts, rock, rap and pop all come from the same place – the blues. They aim to be equal-opportunity popular music historians at the Rock Hall.

“Everyone has their own definition of rock’n'roll,” Henke says. “It’s one of the things we encounter every day at the museum. One encounter that really struck in my mind was back a few years ago, we had a big U2 exhibit here, and I remember a couple visitors coming up and saying, ‘What’s U2 doing here? They’re not rock’n'roll!’ I thought to myself, ‘Well, if U2′s not rock’n'roll, I don’t know who is!’”

Henke continues: “I think what makes us different from other museums is that people come in here and regardless of how much knowledge they have about music, they tend to think of themselves as experts on the subject of pop culture. Take art museums, for example: People don’t go in thinking they know everything there is to know about art. They expect to learn something new. Here, it’s a little bit different — everyone wants to believe they’re an expert in the field.”

Both actual music experts and those who simply fancy themselves music experts will be on hand Saturday (April 14), as the Rock Hall inductions take place in Cleveland.