Many Chinese take pride in China hosting the Olympics, but they're also looking beyond to 2010 when Shanghai will host Expo 2010. This man says it's a great opportunity to exchange knowledge and learn from each other. The expo is expected to stretch three and a half miles along a river when it's finished. In a building, a construction manager shows a scale model of the expo and points out important buildings. So far the American pavilion is one on paper only because the US hasn't signed on to take part in the expo. this official says China wishes the US will be present. That the US has declined to play a role in this huge event doesn't surprise this historian and an expert on world's fairs, and he says the US has a history of showing ambivalence towards world expo movements. Many suspects politics play a role in that ambivalence. This official says these actions aren't helping the US's image abroad. But US officials may not be persuaded by this argument. this professor of public diplomacy says the US's ambivalence would be a mistake. He says world expos should not be confused with world trade fairs, and labor unions and labor would benefit most, a relationship which would benefit both sides, according to this Chinese official.