Wall Street-like exchanges have revolutionized online advertising, but Google is taking the concept further, quietly building one for buying and selling data, the lifeblood of online advertising.

The exchange, known internally by the acronym "DDP," is an attempt to create a liquid market for the data used to target display advertising, and it's the latest move in Google's attempt to build out the infrastructure that powers digital ads. Executives familiar with Google's plans have described the initiative as one of the most ambitious in Google's march to become a brand advertising giant.

Google declined to comment on the specifics or offer a timetable for a data-exchange product, though executives briefed on their plans believe it is perhaps weeks away from rolling out at least some of its functionality.