Abstract: A data processing system for implementing transaction management of auction-based trading is disclosed. The disclosed data processing system provides a structured trading protocol implemented through a sequence of trading paradigms. The system employs a distributed computer processing network linking together a matching engine and a plurality of workstations. The protocol and its programmed controlling logic enhances trading efficiency, rewards market makers, and fairly distributes market opportunity to system users. In some preferred embodiments, the structured trading protocol permits traders to enter hidden bids or offers during a clearing period that may be converted to transactable bids and offers when the clearing period terminates. In addition, in some preferred embodiments, the structured protocol permits traders to enter orders that specify an initial price and a better, hidden price.