US President Barack Obama walked down the gangway in Shanghai last night to begin his visit to China, which lasts through Wednesday.

Obviously, he is carrying with him a heavier agenda than his seven predecessors, with his hallmark appeal for "change". But he has arrived with many more positive notes from both sides, despite the differences and challenges that both countries face in their relations.

Obama has arrived better prepared, as both sides worked hard and ensured a smooth transition and a good start in the relationship after he moved into the White House in January.

Most importantly, whereas some of his predecessors met their Chinese counterparts only once every few years, he has met and held talks with President Hu Jintao face-to-face two times at least, in London in April and New York in September.

In addition, he has held three conversations with Hu by telephone since he was elected president last year.

The talks have been rewarding, as the two presidents have agreed that the two countries should work together to build a positive, cooperative and comprehensive relationship, instead of engaging in zero-sum competition.

At the same time, cabinet members from both countries have met extensively and reached consensus that will enhance broader exchanges of views and personnel in almost all sectors of society, ranging from students and scientists to military personnel.

Even though the two presidents have already highlighted shared interest, we expect them to further cement the foundation as they set sights on the 21st century and take the China-US relationship further beyond bilateral issues.

There is no denying that China and the US differ in ideology and political and social systems, as well as in core values and concerns. These differences have kept the two countries estranged for decades and then put their relationship on a roller-coaster ride over the past 30 years.

The two countries have also immediate anxieties, especially in the area of trade.