The semifinal line-ups have been drawn in both the Men's Singles and Women's Singles events of the London Olympics tennis championships. All the four semifinals are scheduled for today.In the Men's section, while Wimbledon champion Roger Federer meets Argentina's Juan Martin del Potro, Novak Djokovic of Serbia takes on Andy Murray of Britain.In the women singles, while American Serena Williams faces world number one Victoria Azarenka, Russian Maria Sharapova will play against compatriot Maria Kirilenko.