Computer Science Department
School of Computer Science, Carnegie Mellon University


Supporting Online Services in Environments
Constrained by Communication

Arup Mukherjee

November 1998

Ph.D. Thesis

Keywords: Mobile computing, control-oriented programming, World Wide Web, proxies, constrained communication

With the recent rapid growth of the World Wide Web, the advent of commodity internet access via modems, and the slower but steady proliferation of mobile computing devices, more and more users are accessing internet services from computationally capable machines connected via low-speed communication links. While many such services only offer access to static, unchanging documents, the number of ``online'' services offering access to frequently updated information is growing rapidly. While systems have been developed to optimize document access in the presence of constrained communication, their approaches do not handle access to online services well.

This thesis examines the problem of designing online services to be accessed over constrained communication links by computationally capable clients. A taxonomy of application classes has been developed to define the distinguishing characteristics of online services, and recognizes that clients and applications often interact not just to exchange data, but also to control each other's actions or resources. This recognition is the basis for two new models of application structure. The two models are proposed as alternatives to established models and form the basis for the application structuring techniques developed and evaluated.

Support for these application structures has been implemented by the Oasis system, which has been designed to allow the easy deployment of online services as applications within the existing framework of the World Wide Web. An examination of some Oasis applications has demonstrated the qualitative and quantitative advantages of control-oriented design as a flexible approach to reducing the communication requirements of online services. For example, a weather data browser designed explicitly to take advantage of Oasis, when partitioned in a control-oriented manner, was able to eliminate 95% of the steady-state communication usage of alternative implementations. Opportunities for smaller reductions in communication usage have also been observed by proxying communications and automatically leveraging the Oasis infrastructure without explicit application support.

119 pages

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