Computer-Mediated Communication and Ecclesiological Challenges To and From the Reformed Tradition

Communities of faith have appeared online since the inception of computer -­ mediated communication (CMC)and are now ubiquitous. Yet the character and legitimacy of Internet communities as ecclesial bodies is often disputed by traditional churches; and the Internet's ability to host the church as church for online Christians remains a question. This dissertation carries out a practical theological conversation between three main sources: the phenomenon of the church online; ecclesiology (especially that characteristic of Reformed communities); and communication theory. After establishing the need for this study in Chapter 1, Chapter 2 investigates the online presence of Christians and trends in their Internet use, including its history and current expressions. Chapter 3 sets out an historical overview of the Reformed Tradition, focusing on the work of John Calvin and Karl Barth, as well as more contemporary theologians. With a theological context in which to consider online churches in place, Chapter 4 introduces four theological themes prominent in both ecclesiology and CMC studies: authority; community; mediation; and embodiment. These themes constitute the primary lens through which the dissertation conducts a critical-­confessional interface between communication theory and ecclesiology in the examination of CMC. Chapter 5 continues the contextualization of online churches with consideration of communication theories that impact CMC, focusing on three major communication theories: Narrative Theory; Interpretive Theory; and Speech Act Theory. Chapter 6 contains the critical conversation between ecclesiology and communication theory by correlating the aforementioned communication theories with Narrative Theology, Communities of Practice, and Theo-­Drama, and applying these to the four theological themes noted above. In addition, new or anticipated developments in CMC investigated in relationship to traditional ecclesiologies and the prospect of cyber-­ecclesiology. Chapter 7 offers an evaluative tool consisting of a three-­step hermeneutical process that examines: 1) the history, tradition, and ecclesiology of the particular community being evaluated; 2) communication theories and the process of religious-­social shaping of technology; and 3) CMC criteria for establishing the presence of a stable, interactive, and relational community. As this hermeneutical process unfolds, it holds the church at the center of the process, seeking a contextual yet faithful understanding of the church.

An Implementation of Mermera: A Shared Memory System that Mixes Coherence with Non-coherence

Coherent shared memory is a convenient, but inefficient, method of inter-process communication for parallel programs. By contrast, message passing can be less convenient, but more efficient. To get the benefits of both models, several non-coherent memory behaviors have recently been proposed in the literature. We present an implementation of Mermera, a shared memory system that supports both coherent and non-coherent behaviors in a manner that enables programmers to mix multiple behaviors in the same program[HS93]. A programmer can debug a Mermera program using coherent memory, and then improve its performance by selectively reducing the level of coherence in the parts that are critical to performance. Mermera permits a trade-off of coherence for performance. We analyze this trade-off through measurements of our implementation, and by an example that illustrates the style of programming needed to exploit non-coherence. We find that, even on a small network of workstations, the performance advantage of non-coherence is compelling. Raw non-coherent memory operations perform 20-40~times better than non-coherent memory operations. An example application program is shown to run 5-11~times faster when permitted to exploit non-coherence. We conclude by commenting on our use of the Isis Toolkit of multicast protocols in implementing Mermera.

Fast Approximate Reconciliation of Set Differences

We present new, simple, efficient data structures for approximate reconciliation of set differences, a useful standalone primitive for peer-to-peer networks and a natural subroutine in methods for exact reconciliation. In the approximate reconciliation problem, peers A and B respectively have subsets of elements SA and SB of a large universe U. Peer A wishes to send a short message M to peer B with the goal that B should use M to determine as many elements in the set SB–SA as possible. To avoid the expense of round trip communication times, we focus on the situation where a single message M is sent. We motivate the performance tradeoffs between message size, accuracy and computation time for this problem with a straightforward approach using Bloom filters. We then introduce approximation reconciliation trees, a more computationally efficient solution that combines techniques from Patricia tries, Merkle trees, and Bloom filters. We present an analysis of approximation reconciliation trees and provide experimental results comparing the various methods proposed for approximate reconciliation.