Rock & Roll

I was just reading this article and it made me think about some things.

What exactly is Rock & Roll?
Is Madonna rock & roll? According to the hall of fame she is. What about Grandmaster Flash? What makes R&B/Rap/Pop artists eligible for the Rock & Roll Hall of Fame? Should it even be called the Rock & Roll Hall of Fame? I suppose it is a matter of semantics, as they say in the article, but it brings up good questions.

So back to my first question. What is rock & roll? According to an online dictionary the definition is:
rock·-and-roll (räk′'n rōl′)

noun

a form of popular music that evolved in the 1950s from rhythm and blues, characterized by the use of electric guitars, a strong rhythm with an accent on the offbeat, and youth-oriented lyrics

So, according to this definition there need to be electric guitars, strong rhythm, and youth oriented lyrics. How many genres does that span in music today? Should any artist that fits this description be allowed access into the hall of fame?

What are your thoughts? What do you think makes Rock & Roll?