This paper presents an approach to translating the data associated with a problem-solving procedure into efficient implementations. The approach involves reduction of problem-domain data strutures to implementations by way of intermediate modelling structures. Formalists are introduced for describing modelling structures -- abstract representations of data characteristics and relationships, independent of any specific implemetation -- and implementation structures -- machine-processable represetations. Based upon these formalisms, algorithms are presented for recognizing known modelling structures, for synthesizing implementations for modelling structures not recognized, and for combining several implementations according to structure membership and variable binding relationships. Design considerations influencing these formalisms and algorithms are discussed.

A storage structures formalism is described which can be used as a precise symbolic representation of low-level storage organizations and also as a description of storage requirements to a storage allocation mechanism. The formalism is based on three forms of memory management (sequential, linked, and associative) and associated referencing mechanisms (indexing, pointing, and hashing). Several examples of the formalism are presented. The meaning, or interpretation, of a storage structure as used to implement a modelling structure is discussed. Examples of alternative implementation structures (storage structures and their interpretations) for a particular modelling structure are presented.

The Berkeley Internet Broadcasting System (BIBS) is a lecture webcasting system developed and operated by the Berkeley Multimedia Research Center. The system offers live remote viewing and on-demand replay of course lectures using streaming audio and video over the Internet. During the Fall 2000 semester 14 classes were webcast, including several large lower division classes, with a total enrollment of over 4,000 students. Lectures were played over 15,000 times per month during the semester. The primary use of the webcasts is to study for examinations. Students report they watch BIBS lectures because they did not understand material presented in lecture, because they wanted to review what the instructor said about selected topics, because they missed a lecture, and/or because they had difficulty understanding the speaker (e.g., non-native English speakers). Analysis of various survey data suggests that more than 50% of the students enrolled in some large classes view lectures and that as many as 75% of the lectures are played by members of the Berkeley community. Faculty attitudes vary about the virtues of lecture webcasting. Some question the use of this technology while others believe it is a valuable aid to education. Further study is required to accurately assess the pedagogical impact that lecture webcasts have on student learning.

This paper describes a design for a computing system structure whose implementation should provide reliable, faiI-soft service at relativeIy Iow cost. The design reIies heavily on modularity and dynamic reconfigurability (in combination referred to as distribution) to achieve reliability. Low cost is maintainted by using standard hardware and software components, each of which handles a portion of the workload. When a component fails, its workload is assumed by the remaining components. The evolution of a particular network architecture for this computing system, i.e., a network utilizing a communication loop with hardware components connected to and distributed about the ring, is described.

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