Server-directed transcoding

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, sewer-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. (C) 2001 Elsevier Science B.V. All rights reserved.