We present a new Web middleware architecture that allows users to customize their view of the Web for optimal interaction and system operation when using non-traditional resource-limited client machines such as wireless PDAs (personal digital assistants). Web Stream Customizers (WSC) are dynamically deployable software modules and can be strategically located between client and server to achieve improvements i n performance, reliability, or security. An important design feature is that Customizers provide two points of control in the communication path between client and server, supporting adaptive system-based and content-based customization. Our architecture exploits HTTP's proxy capabilities, allowing Customizers to be seamlessly integrated with the basic Web transaction model. We describe the WSC architecture and implementation, and illustrate its use with three non-trivial, adaptive Customizer applications that we have built. We show that the overhead in our implementation is small and tolerable, and is outweighed by the benefits that Customizers provide.

Declustered data organizations in disk arrays

Abstract-We present network flow buffering, which is the use of a remote flow-regulating buffer that is deployed between a Web client and server to improve performance of HTTP-based playback of video. We show that HTTP enhanced with network flow buffering significantly improves performance, especially under high packet loss and highly variable bandwidth conditions, when compared with using either straight HTTP or streaming. The benefits of network flow buffering are numerous, and include reducing interruptions to playback, maintaining high video-image quality, and decreasing client-buffering requirements. Network flow buffering is easily implemented with existing Web mechanisms.

We present improvements to a Web middleware system that supports flexible Web content and stream customizations such as filtering, compression, encryption, remote caching, and remote buffering, especially applicable for wireless Web access. The new extensions provide support for user relocation, and make the system more practical by emphasizing the use of a personal server for running customization modules and for maintaining user configuration and application data, in addition to the selected use of third party servers to bolster performance, increase fault tolerance, and satisfy special security requirements.

Abstract-We present the design of the Web Stream Customizer Architecture, the basis for a middleware system that supports customization of Web content and streams. Our notion of customization is quite general, including functions such as filtering, remote buffering, remote caching, flow regulation (e.g., for video playback), compression, and encryption, all of which are especially valuable for wireless resource-limited clients, which are a primary target of support. The system is highly deployable, as it works entirely within the Web's common programming and communication frameworks, such as using HTTP and relying solely on standard proxy mechanisms, and therefore does not require any changes to existing Web servers and browsers.