You mean Miami’s not world-class yet?

It was the cliche of the boom years in Miami: World Class City. It seemed the performing arts center would get us there, or the port tunnel, or the museums, or all those condo towers.

And while promising, it’s clear downtown Miami’s revival has not yet fully jelled, and it’s not only the real estate crash that’s to blame. The place is still somewhere south of real urban livability, despite encouraging signs of verve.

So how can downtown Miami's revival interruptus be extended and sustained?

Maybe we’ll find out from some of the country's leading urban revivalists Thursday, when the Greater Miami Chamber of Commerce hosts a public forum on the question.

Speakers at the symposium, titled ‘’The Making of a Modern City: How to Take Miami to the Next Level,’’ include Joseph Riley, the former Charleston, S.C., mayor credited with that city's resuscitation, and former Pittsburgh Mayor Tom Murphy, who launched a wide-ranging downtown revitalization in his town.

Eugenie Birch, an urban planning historian at the University of Pennsylvania, will also be on the panel, to be moderated by Miami architect and planner Bernard Zyscovich.

Registration is $45 for members; $55 for nonmembers in advance, $60 at the door. Online registration is available at www.miamichamber.com. Registration and breakfast begin at 7:45 a.m., followed by the program from 8:15 to 10:30 a.m. at the Hilton Hotel at 1601 Biscayne Blvd.