Start-up Gravity is rolling out its ambitious advertising concepts at this week's Web 2.0 Summit.

The foundation of the company's pitch is quite simple: CEO Amit Kapur says Gravity knows what you like and what you want better than any search engine. That information, of course, is gold to advertisers.

How Gravity gets that data and the theories behind it are a bit more complex than the simple pitch. Gravity has created an ontology of interests. Underneath all the company's data-mining technology is a database of about 4,000 concepts that are connected to 7.5 million "interests" and 100 million colloquial phrases. Human "ontology monkeys" (my term, not Kapur's), algorithms, and eventually crowdsourcing will keep the ontology up to date.

When you use one of these 100 million phrases in a social update--a Facebook post, a tweet, or a blog entry--Gravity notes which concepts you're talking about and files them under your name. Likewise, when you include a link to a Web page in an update, Gravity divines the top concepts from that page and those go in your profile too.