Brian Barth and his team of five data divers knew the software they developed had potential. For something. As Barth explained one day in 1999 to a buddy from his M.I.T. rowing days, he had an Internet search engine that could reach far into dynamic databases and cope with constantly churning information. His friend, then working in the airline industry, gave Barth the news: "Don't you realize? This is the Holy Grail of travel. They've wanted to do this forever."
Thus emerged Sidestep, Barth's two-month-old company, which joins second-generation dotcom travel sites like QIXO and Farechase in a challenge to such...