The World Wide Web has succeeded in large part because its software architecture has been designed to meet the needs of an Internet-scale distributed hypermedia application. The modern Web architecture emphasizes scalability of component interactions, generality of interfaces, independent deployment of components, and intermediary components to reduce interaction latency, enforce security, and encapsulate legacy systems. In this article we introduce the Representational State Transfer (REST) architectural style, developed as an abstract model of the Web architecture and used to guide our redesign and definition of the Hypertext Transfer Protocol and Uniform Resource Identifiers. We describe the software engineering principles guiding REST and the interaction constraints chosen to retain those principles, contrasting them to the constraints of other architectural styles. We then compare the abstract model to the currently deployed Web architecture in order to elicit mismatches between the existing protocols and the applications they are intended to support.

Principled design of the modern Web architecture

The World Wide Web has succeeded in large part because its software architecture has been designed to meet the needs of an Internet-scale distributed hypermedia system. The modern Web architecture emphasizes scalability of component interactions, generality of interfaces, independent deployment of components, and intermediary components to reduce interaction latency, enforce security, and encapsulate legacy systems. In this paper, we introduce the Representational State Transfer (REST) architectural style, developed as an abstract model of the Web architecture to guide our redesign and definition of the Hypertext Transfer Protocol and Uniform Resource Identifiers. We describe the software engineering principles guiding REST and the interaction constraints chosen to retain those principles, contrasting them to the constraints of other architectural styles. We then compare the abstract model to the currently deployed Web architecture in order to elicit mismatches between the existing protocols and the applications they are intended to support.

/pdf/principled-design-of-the-modern-web-architecture-1hhuhjnc21.pdf

We identify three fundamental requirements for scalable network services: incremental scalability and overflow growth provisioning, 24x7 availability through fault masking, and cost-effectiveness. We argue that clusters of commodity workstations interconnected by a high-speed SAN are exceptionally well-suited to meeting these challenges for Internet-server workloads, provided the software infrastructure for managing partial failures and administering a large cluster does not have to be reinvented for each new service. To this end, we propose a general, layered architecture for building cluster-based scalable network services that encapsulates the above requirements for reuse, and a service-programming model based on composable workers that perform transformation, aggregation, caching, and customization (TACC) of Internet content. For both performance and implementation simplicity, the architecture and TACC programming model exploit BASE, a weaker-than-ACID data semantics that results from trading consistency for availability and relying on soft state for robustness in failure management. Our architecture can be used as an off the shelf infrastructural platform for creating new network services, allowing authors to focus on the content of the service (by composing TACC building blocks) rather than its implementation. We discuss two real implementations of services based on this architecture: TranSend, a Web distillation proxy deployed to the UC Berkeley dialup IP population, and HotBot, the commercial implementation of the Inktomi search engine. We present detailed measurements of TranSend's performance based on substantial client traces, as well as anecdotal evidence from the TranSend and HotBot experience, to support the claims made for the architecture.

https://pages.cs.wisc.edu/~remzi/Classes/736/Fall2007/Papers/tacc.pdf

Cluster-based scalable network services

Process migration is the act of transferring a process between two machines. It enables dynamic load distribution, fault resilience, eased system administration, and data access locality. Despite these goals and ongoing research efforts, migration has not achieved widespread use. With the increasing deployment of distributed systems in general, and distributed operating systems in particular, process migration is again receiving more attention in both research and product development. As high-performance facilities shift from supercomputers to networks of workstations, and with the ever-increasing role of the World Wide Web, we expect migration to play a more important role and eventually to be widely adopted.This survey reviews the field of process migration by summarizing the key concepts and giving an overview of the most important implementations. Design and implementation issues of process migration are analyzed in general, and then revisited for each of the case studies described: MOSIX, Sprite, Mach, and Load Sharing Facility. The benefits and drawbacks of process migration depend on the details of implementation and, therefore, this paper focuses on practical matters. This survey will help in understanding the potentials of process migration and why it has not caught on.

Process migration

Recent advances in wireless data networking and portable information appliances have engendered a new paradigm of computing, called mobile computing, in which users carrying portable devices have access to data and information services regardless of their physical location or movement behavior. In the meantime, research addressing information access in mobile environments has proliferated. In this survey, we provide a concrete framework and categorization of the various ways of supporting mobile client-server computing for information access. We examine characteristics of mobility that distinguish mobile client-server computing from its traditional counterpart. We provide a comprehensive analysis of new paradigms and enabler concepts for mobile client-server computing, including mobile-aware adaptation, extended client-server model, and mobile data access. A comparative and detailed review of major research prototypes for mobile information access is also presented.

/pdf/client-server-computing-in-mobile-environments-3vod22mkor.pdf

Client-server computing in mobile environments

Application-Specific Proxy Servers as HTTP Stream Transducers.

This paper describes an innovative approach for groups to create and share commentary about the content of documents accessible via the World Wide Web. In particular, the system described supports the creation, presentation, and control of user-created meta-information, which is displayed with the corresponding documents but stored separately from them. The typical use for this mechanism is to support annotations about documents accessed through browsing clients of the Web. In contrast to other approaches, the system described herein does not depend on changes in, or specializations to, Web browsers or servers. Rather, the system takes advantage of the notion of application-specific stream transducers ; most of the functionality of the system is provided by a specialized proxy. We describe design considerations, the system architecture, usage scenarios, our initial implementation, and future work.

Pan-browser support for annotations and other meta-information on the World Wide Web

Caubview is a companion visualizer for the Caubweb system: Caubweb enables a user to create a local collection of Web documents to read and update when disconnected. Caubview allows the visual selection of alternative views of the cache as well as reorganizing and restructuring these views. This paper describes our ongoing work on the Caubweb system, focusing on its visualization component, Caubview. We describe the relationship between these two systems, how we developed Caubview by re-using code from the HistoryGraph application, our results, and our plans for further development. We further describe our experiences using Tcl/Tk as the development language and "programming culture" for these applications, and indicate how ongoing developments in Tcl/Tk have influenced our work. We conclude with some observations concerning our future use of Tcl/Tk, and recommendations for ongoing efforts for the Tcl/Tk community.

/pdf/visualizing-personal-web-caches-with-caubview-2zjnuvrex0.pdf

Murray S. Mazer

Papers

Application-Specific Proxy Servers as HTTP Stream Transducers.

Pan-browser support for annotations and other meta-information on the World Wide Web

Visualizing personal web caches with Caubview