Transcoding, the conversion between different representations of Web content at an intermediate proxy, can ameliorate mismatches between the complex content provided by an origin server, and the limited bandwidth to, or display capabilities of, a Web client. Existing transcoding systems use implicit information, such as the HTTP Content-type, to control when and how they convert between representations. This approach must balance the risk of losing important information against the intended goal (such as bandwidth reduction), often without sufficient information to make the optimal choice.

A new approach, "server-directed transcoding," uses explicit guidance from the server to allow a transcoding proxy to make the best possible choice. This paper describes several possible approaches to server-directed transcoding, including "transcoding applets," the use of mobile code to provide the origin server detailed control over transcoding performed by proxies. The paper discusses security, caching, and other operational issues associated with transcoding applets.

About Jeffrey C. Mogul

Jeffrey C. Mogul received an S.B. from the Massachusetts Institute of Technology in 1979, an M.S. from Stanford University in 1980, and his PhD from the Stanford University Computer Science Department in 1986. Dr. Mogul has been an active participant in the Internet community, and is the author or co-author of several Internet Standards; most recently, he has contributed extensively to the HTTP/1.1 specification. Since 1986, he has been a researcher at the Compaq (formerly Digital) Western Research Laboratory, working on network and operating systems issues for high-performance computer systems, and on improving performance of the Internet and the World Wide Web. He is a member of ACM, Sigma Xi, and CPSR, and was Program Committee Chair for the Winter 1994 USENIX Technical Conference, and for the IEEE TCOS Sixth Workshop on Hot Topics in Operating Systems.