Abstract: A method for facilitating the trading of media space includes collecting, by a server node, an offer of an ad avail from a seller and a request for an ad avail by a buyer. The offer is in effect for a fixed time period and includes a first price at the commencement of the fixed time period and a second price at the end of the fixed time period. A price-time relationship for the ad avail is specified by the seller such that the price of the ad avail varies over the fixed time period. The server node matches the request to the offer at time t1 during the fixed time period and the server node computes a price for the ad avail based on t1 using the price-time function.