Systems support for distributed learning environments

This thesis contends that the growing phenomena of multi-user networked "learning environments" should be treated as distributed interactive systems and that their developers should be aware of the systems and networks issues involved in their construction and maintenance. Such environments are henceforth referred to as distributed learning environments, or DLEs. Three major themes are identified as part of systems support: i) shared resource coherence in DLEs; ii) Quality of Service for the end- users of DLEs; and iii) the need for an integrating framework to develop, deploy and manage DLEs. The thesis reports on several distinct implementations and investigations that are each linked by one or more of those themes. Initially, responsiveness and coherence emerged as potentially conflicting requirements, and although a system was built that successfully resolved this conflict it proved difficult to move from the "clean room" conditions of a research project into a real world learning context. Accordingly, subsequent systems adopted a web-based approach to aid deployment in realistic settings. Indeed, production versions of these systems have been used extensively in credit-bearing modules in several Scottish Universities. Interactive responsiveness then emerged as a major Quality of Service issue in its own right, and motivated a series of investigations into the sources of delay, as experienced by end users of web-oriented distributed learning environments. Investigations into this issue provided insight into the nature of web-oriented interactive distributed learning and highlighted the need to be QoS-aware. As the volume and the range of usage of distributed learning applications increased the need for an integrating framework emerged. This required identifying and supporting a wide variety of educational resource types and also the key roles occupied by users of the system, such as tutors, students, supervisors, service providers, administrators, examiners. The thesis reports on the approaches taken and lessons learned from researching, designing and implementing systems which support distributed learning. As such, it constitutes a documented body of work that can inform the future design and deployment of distributed learning environments

Efficient Passive Clustering and Gateways selection MANETs

Passive clustering does not employ control packets to collect topological information in ad hoc networks. In our proposal, we avoid making frequent changes in cluster architecture due to repeated election and re-election of cluster heads and gateways. Our primary objective has been to make Passive Clustering more practical by employing optimal number of gateways and reduce the number of rebroadcast packets

Political artifacts and personal privacy : the Yenta multi-agent distributed matchmaking system

Thesis (Ph.D.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 1999.Includes bibliographical references (p. 119-128).Technology does not exist in a social vacuum. The design and patterns of use of any particular technological artifact have implications both for the direct users of the technology, and for society at large. Decisions made by technology designers and implementors thus have political implications that are often ignored. If these implications are not made a part of the design process, the resulting effects on society can be quite undesirable. The research advanced here therefore begins with a political decision: It is almost always a greater social good to protect personal information against unauthorized disclosure than it is to allow such disclosure. This decision is expressly in conflict with those of many businesses and government entities. Starting from this premise, a multi-agent architecture was designed that uses both strong cryptography and decentralization to enable a broad class of Internet-based software applications to handle personal information in a way that is highly resistant to disclosure. Further, the design is robust in ways that can enable users to trust it more easily: They can trust it to keep private information private, and they can trust that no single entity can take the system away from them. Thus, by starting with the explicit political goal of encouraging well-placed user trust, the research described here not only makes its social choices clear, it also demonstrates certain technical advantages over more traditional approaches. We discuss the political and technical background of this research, and explain what sorts of applications are enabled by the multi-agent architecture proposed. We then describe a representative example of this architecture--the Yenta matchmaking system. Yenta uses the coordinated interaction of large numbers of agents to form coalitions of users across the Internet who share common interests, and then enables both one-to-one and group conversations among them. It does so with a high degree of privacy, security, and robustness, without requiring its users to place unwarranted trust in any single point in the system.by Leonard Newton Foner.Ph.D

Resilient architecture (preliminary version)

The main objectives of WP2 are to define a resilient architecture and to develop a range of middleware solutions (i.e. algorithms, protocols, services) for resilience to be applied in the design of highly available, reliable and trustworthy networking solutions. This is the first deliverable within this work package, a preliminary version of the resilient architecture. The deliverable builds on previous results from WP1, the definition of a set of applications and use cases, and provides a perspective of the middleware services that are considered fundamental to address the dependability requirements of those applications. Then it also describes the architectural organisation of these services, according to a number of factors like their purpose, their function within the communication stack or their criticality/specificity for resilience. WP2 proposes an architecture that differentiates between two classes of services, a class including timeliness and trustworthiness oracles, and a class of so called complex services. The resulting architecture is referred to as a "hybrid architecture". The hybrid architecture is motivated and discussed in this document. The services considered within each of the service classes of the hybrid architecture are described. This sets the background for the work to be carried on in the scope of tasks 2.2 and 2.3 of the work package. Finally, the deliverable also considers high-level interfacing aspects, by providing a discussion about the possibility of using existing Service Availability Forum standard interfaces within HIDENETS, in particular discussing possibly necessary extensions to those interfaces in order to accommodate specific HIDENETS services suited for ad-hoc domain

Design principles and patterns for computer systems that are simultaneously secure and usable

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (p. 429-464) and index.It is widely believed that security and usability are two antagonistic goals in system design. This thesis argues that there are many instances in which security and usability can be synergistically improved by revising the way that specific functionality is implemented in many of today's operating systems and applications. Specific design principles and patterns are presented that can accomplish this goal. Patterns are presented that minimize the release of confidential information through remnant and remanent data left on hard drives, in web browsers, and in documents. These patterns are based on a study involving the purchase of 236 hard drives on the secondary market, interviews conducted with organizations whose drives had been acquired, and through a detailed examination of modern web browsers and reports of information leakage in documents. Patterns are presented that enable secure messaging through the adoption of new key management techniques. These patterns are supported through an analysis of S/MIME handling in modern email clients, a survey of 469 Amazon.com merchants, and a user study of 43 individuals. Patterns are presented for promoting secure operation and for reducing the danger of covert monitoring. These patterns are supported by the literature review and an analysis of current systems.(cont.) In every case considered, it is shown that the perceived antagonism of security and usability can be scaled back or eliminated by revising the underlying designs on which modern systems are conceived. In many cases these designs can be implemented without significant user interface changes. The patterns described in this thesis can be directly applied by today's software developers and used for educating the next generation of programmers so that longstanding usability problems in computer security can at last be addressed. It is very likely that additional patterns can be identified in other related areas.by Simson L. Garfinkel.Ph.D

Combining SOA and BPM Technologies for Cross-System Process Automation

This paper summarizes the results of an industry case study that introduced a cross-system business process automation solution based on a combination of SOA and BPM standard technologies (i.e., BPMN, BPEL, WSDL). Besides discussing major weaknesses of the existing, custom-built, solution and comparing them against experiences with the developed prototype, the paper presents a course of action for transforming the current solution into the proposed solution. This includes a general approach, consisting of four distinct steps, as well as specific action items that are to be performed for every step. The discussion also covers language and tool support and challenges arising from the transformation

A hardware-software codesign framework for cellular computing

Until recently, the ever-increasing demand of computing power has been met on one hand by increasing the operating frequency of processors and on the other hand by designing architectures capable of exploiting parallelism at the instruction level through hardware mechanisms such as super-scalar execution. However, both these approaches seem to have reached a plateau, mainly due to issues related to design complexity and cost-effectiveness. To face the stabilization of performance of single-threaded processors, the current trend in processor design seems to favor a switch to coarser-grain parallelization, typically at the thread level. In other words, high computational power is achieved not only by a single, very fast and very complex processor, but through the parallel operation of several processors, each executing a different thread. Extrapolating this trend to take into account the vast amount of on-chip hardware resources that will be available in the next few decades (either through further shrinkage of silicon fabrication processes or by the introduction of molecular-scale devices), together with the predicted features of such devices (e.g., the impossibility of global synchronization or higher failure rates), it seems reasonable to foretell that current design techniques will not be able to cope with the requirements of next-generation electronic devices and that novel design tools and programming methods will have to be devised. A tempting source of inspiration to solve the problems implied by a massively parallel organization and inherently error-prone substrates is biology. In fact, living beings possess characteristics, such as robustness to damage and self-organization, which were shown in previous research as interesting to be implemented in hardware. For instance, it was possible to realize relatively simple systems, such as a self-repairing watch. Overall, these bio-inspired approaches seem very promising but their interest for a wider audience is problematic because their heavily hardware-oriented designs lack some of the flexibility achievable with a general purpose processor. In the context of this thesis, we will introduce a processor-grade processing element at the heart of a bio-inspired hardware system. This processor, based on a single-instruction, features some key properties that allow it to maintain the versatility required by the implementation of bio-inspired mechanisms and to realize general computation. We will also demonstrate that the flexibility of such a processor enables it to be evolved so it can be tailored to different types of applications. In the second half of this thesis, we will analyze how the implementation of a large number of these processors can be used on a hardware platform to explore various bio-inspired mechanisms. Based on an extensible platform of many FPGAs, configured as a networked structure of processors, the hardware part of this computing framework is backed by an open library of software components that provides primitives for efficient inter-processor communication and distributed computation. We will show that this dual software–hardware approach allows a very quick exploration of different ways to solve computational problems using bio-inspired techniques. In addition, we also show that the flexibility of our approach allows it to exploit replication as a solution to issues that concern standard embedded applications