Exchange order priority retention for electronic trading using automatic book updates

A method comprising:

• taking a user's desired position of a tradable item, wherein the desired position is depicted in a user target trading book that includes an identifier of the tradable item, a side of the market for the tradable item, a quantity of the tradable item, and a price;
• retrieving with a processor actual order data of the user for the tradable item, the actual order data being retrieved from a data storage facility that is accessible to the processor, the actual order data representing one or more unmatched orders pending on an exchange;
• calculating with the processor a difference between the user's desired position and the user's actual order data to determine one or more order actions to effect a transition of the user's actual trading book to the user's target trading book;
• and
• submitting electronically to the exchange at least one of the one or more order actions that leaves the oldest possible unmatched orders based on time stamp remaining on the exchange.

A trading system, comprising:

• first data stored in a processor accessible memory representing a user target trading book, the data including a user's desired position of a tradable item comprising an identifier of the tradable item, a side of the market for the tradable item, a quantity of the tradable item, and a price;
• second data stored in a processor accessible memory representing unmatched trade orders on an exchange of the user for the tradable item;
• and
• computer software stored in a processor accessible memory that when executed by the processor compares the first data to the second data and identifies an order action to be electronically submitted to the exchange to establish on the exchange a set of unmatched trade orders for the user that reflect the user's desired position while maintaining on the exchange an unmatched order of the user with the oldest possible time stamp.