Defining SEFs: The Commodity Futures Trading Commission and the Securities and Exchange Commission still differ on what a "swap execution facility" (SEF) should look like. So what are the prospects for compromise? Richard McVey, chief executive of MarketAxess, a bond and derivatives trading platform, discusses with Jeremy Grant the sticking points between the two regulators in trying to find a compromise between greater transparency and maintaining liquidity, and the risks to derivatives trading of a 'big bang' implementation.