Pittsburgh Mayor Luke Ravenstahl announced today that the city would challenge the tax exempt status of regional medical giant UPMC, a court battle that he likened to "the David versus the Goliath." "They're not a charity," the mayor said at a press conference today. "They haven't been operating as a charity and it's time that this community step up in that regard. The reality of the situation is the taxpayers ... are currently subsidizing UPMC's non-profit status." The mayor said he was emboldened to make the challenge by a Pennsylvania Supreme Court decision last year that reaffirmed tax-exempt organizations must meet five criteria outlined in a previous court case, including one that requires them to operate without profit motive.