A Communication Framework for Digital Libraries

Digital libraries involve various types of data like text, audio, images and video. The data objects are typically very large and of the order of hundreds and thousands of kilobytes. In a digital library, these data objects are distributed in a wide area network. Retrieving large data objects in a wide area network has a high response time. We have conducted experiments to measure the communication overhead in the response time. We have studied the correlation between communication and size of data, between communication and type of data and the communication delay to various sites in a local and wide area network. We present different strategies for reducing delay while communicating multimedia data. Images are amenable to losing data without losing semantics of the image. Lossy compression techniques reduce the quality of the image and reduce the size leading to a lower communication delay. We compared the communication delay between compressed and uncompressed images and study the overhead due to compression and decompression. We present issues in providing digital library service to mobile users and discuss a question: What if communication were free? Finally, we present a framework for efficient communication of digital library data.