Abstract: A data transmission system which optimizes transfer and updates of information between systems by providing difference information between the systems is disclosed. Information transfer can occur one way (broadcast) or two-way (sync). In a first aspect, the system includes a differencing transmitter transmitting at least one set of difference transactions and a differencing receiver receiving said at least one set of difference transactions. The differencing transmitter of the data transmission system may comprise a difference source interface, a copy of a previous state of said difference source, and a difference transaction generator. The differencing receiver of the data transmission system comprises a difference destination interface, a copy of a previous state of said difference destination, and a destination data constructor. In a further embodiment, the data transmission system is coupled to a network.