The presentation of multimedia data in a distributed database environment require good quality of service for real-time data transmission. However, even if the required resources are guaranteed at all times, various variations in bit rates for compressed streams as well as transmission and retrieval delays may cause unpredictable variations in data transmission rate. Novel end-to-end control approaches are needed to dynamically adjust data flow from databases to remote clients and to guarantee the availability and timeliness of data as demanded.

In addition, the system must be able to dynamically respond to various types of user interactions. We propose to investigate novel approaches between servers, network, and clients to adaptively control data retrieval and transmission.

We consider that the retrieval of data from their source location to destination location must pass four main intermediate locations.

First, the stored data are cached from the disk to the server.

Second, the cached data are transmitted through the network.

Third, the transmitted data are received at the local client cache.

Finally, the locally cached data are displayed on the local machine.

The display controller detects the rate changes that may occur during the presentations of media data and feeds back such changes to the receiver controller. The receiver controller detects the overflow or underflow of the client cache and feeds back such information to the transmit controller. The transmit controller maintains the network transferring rate and feeds back changes to the cache controller which dynamically adjust the disk retrieving rate.