ContextWeb, a contextual advertising firm, has launched its online ad exchange, allowing publishers and advertisers to set firm "Bid" or "Ask" prices.

ContextWeb will trade on behalf of its existing network advertiser and publisher clients when the ADSDAQ exchange formally opens this summer. ADSDAQ will open a self-service trading desk to all publishers upon launch and a similar trading desk to advertisers later this year.

"Successful exchanges have always provided traders the ability to place a firm 'Bid' or 'Ask' price," said Anand Subramanian, CEO of ContextWeb, Inc. "The online marketplace is now ready for a true exchange. By including advertisers and publishers of all sizes, ADSDAQ creates a more scalable marketplace for premium advertising inventory across the entire internet."

According to ContextWeb, ADSDAQ differs from other exchanges such as those operated by Right Media and DoubleClick because its publishers are permitted to set an "Ask" price, a model company officials say stifles market volume and liquidity by allowing only for a remnant inventory pool.

Earlier this month, Tom Hespos, president of Underscore Marketing, said the exchange model might be a viable option in the coming years.