Referencing and retention in block-structured coroutines

technical reportThe combination of coroutines with recursive procedures is characteristic of many modern higher-level languages offering advanced control structures (e.g. SIMULA-67, SL5, Interlisp, etc.). We say a language has block-structured coroutines (BSCRs) when static nesting considerations govern the usage of this control combination. Starting with the BSCR control description work of Wang and Dahl, this paper pursues further the implications of static program structure on BSCR programs in a compilation-oriented setting. Disciplines on BSCR reference assignment and individual control actions are defined, offering enhanced implementability and program comprehensibility. Of particular interest is a scope-based discipline on "detach" operations, which avoids the formation of idle chain subheads, an implementationally undesirable condition. The retention requirements of BSCRs are analyzed under a range of possible remote accessibility conditions, and two deletion strategies are then defined, keyed to these requirements. The first uses a special form of scope-sensitive reference counting, and the second does mark-sweep garbage collection, again exploiting static program structure. Space and time estimates for both methods are given, along with avenues for continuing research

Towards Tamper-Evident Storage on Patterned Media

We propose a tamper-evident storage system based on probe storage with a patterned magnetic medium. This medium supports normal read/write operations by out-of-plane magnetisation of individual magnetic dots. We report on measurements showing that in principle the medium also supports a separate class of write-once operation that destroys the out-of-plane magnetisation property of the dots irreversibly by precise local heating. We discuss the main issues of designing a tamper-evident storage device and file system using the properties of the medium

Impliance: A Next Generation Information Management Appliance

ably successful in building a large market and adapting to the changes of the last three decades, its impact on the broader market of information management is surprisingly limited. If we were to design an information management system from scratch, based upon today's requirements and hardware capabilities, would it look anything like today's database systems?" In this paper, we introduce Impliance, a next-generation information management system consisting of hardware and software components integrated to form an easy-to-administer appliance that can store, retrieve, and analyze all types of structured, semi-structured, and unstructured information. We first summarize the trends that will shape information management for the foreseeable future. Those trends imply three major requirements for Impliance: (1) to be able to store, manage, and uniformly query all data, not just structured records; (2) to be able to scale out as the volume of this data grows; and (3) to be simple and robust in operation. We then describe four key ideas that are uniquely combined in Impliance to address these requirements, namely the ideas of: (a) integrating software and off-the-shelf hardware into a generic information appliance; (b) automatically discovering, organizing, and managing all data - unstructured as well as structured - in a uniform way; (c) achieving scale-out by exploiting simple, massive parallel processing, and (d) virtualizing compute and storage resources to unify, simplify, and streamline the management of Impliance. Impliance is an ambitious, long-term effort to define simpler, more robust, and more scalable information systems for tomorrow's enterprises.Comment: This article is published under a Creative Commons License Agreement (http://creativecommons.org/licenses/by/2.5/.) You may copy, distribute, display, and perform the work, make derivative works and make commercial use of the work, but, you must attribute the work to the author and CIDR 2007. 3rd Biennial Conference on Innovative Data Systems Research (CIDR) January 710, 2007, Asilomar, California, US

Garbage collection in distributed systems

PhD ThesisThe provision of system-wide heap storage has a number of advantages. However, when the technique is applied to distributed systems automatically recovering inaccessible variables becomes a serious problem. This thesis presents a survey of such garbage collection techniques but finds that no existing algorithm is entirely suitable. A new, general purpose algorithm is developed and presented which allows individual systems to garbage collect largely independently. The effects of these garbage collections are combined, using recursively structured control mechanisms, to achieve garbage collection of the entire heap with the minimum of overheads. Experimental results show that new algorithm recovers most inaccessible variables more quickly than a straightforward garbage collection, giving an improved memory utilisation

Teaching and Professional Fellowship Report 2007-2008 : Make the Numbers Count, Improving students' learning experiences through an analysis of Library and Learning Resources data

Feedback on Library and Learning Resources (LLR) services and support at the University of the Arts London (UAL) is received from a very extensive range of sources. However, although a considerable quantity of information is available for analysis, it remains very difficult for LLR staff to extract meaningful data from these numerous sources, which can reveal, in depth, the true, individual student experience of LLR services. LLR is aware that there is a lot that is not known, or is not being asked of our students, about their individual experience, which could prove extremely helpful for effective decision-making and service design and delivery. In particular, LLR is interested in identifying and resolving issues of access and support for students currently studying at UAL who are from under represented groups in higher education. Make the numbers counts has enabled the Fellowship Team to move beyond looking at usage figures, gate counts, numbers of issue and renewal transactions, borrower numbers and percentage satisfaction levels, and to extend and add to our knowledge-base of what students at UAL really think and feel about academic libraries. It has enabled us to explore how individual students make use of the services and support provided by LLR. The qualitative data collected through this project has been compared to existing sources of information and to staff experience and understanding of the issues raised, to see if the findings of our research challenge or correlate with other evidence which relates to LLR use and non-use. The focus of the Fellowship has been to explore the particular experience of students who are the first in their family to go to university and who are currently studying at Camberwell, Chelsea and Wimbledon (CCW) and the London College of Communication. Research has shown that this group of students is important amongst the range of students who are now entering higher education through the expansion of participation in university and tertiary-level study. Talking to first generation students was a key element of the project and the greatest source of learning for the Project Team

A distributed programming environment for Ada

Despite considerable commercial exploitation of fault tolerance systems, significant and difficult research problems remain in such areas as fault detection and correction. A research project is described which constructs a distributed computing test bed for loosely coupled computers. The project is constructing a tool kit to support research into distributed control algorithms, including a distributed Ada compiler, distributed debugger, test harnesses, and environment monitors. The Ada compiler is being written in Ada and will implement distributed computing at the subsystem level. The design goal is to provide a variety of control mechanics for distributed programming while retaining total transparency at the code level

Web Log Data Analysis: Converting Unstructured Web Log Data into Structured Data Using Apache Pig

Data extraction and analysis have recently received significant attention due to the evolution of social media and large volume of data available in an unstructured form. Hadoop and MapReduce have been continuously implementing and analyzing large amount of data. In this paper Apache Pig, which is one of the high-level platform for analyzing large volume of data and runs on the top of Hadoop is used to analyze unstructured log files and extract information. In this paper, weblog server files are used to analyze and extract meaningful information in an unstructured form to a structured form in Apache Pig framework The main purpose of this paper is to extract, transform and load unstructured data in an Apache Pig framework and analyze the data and its performance on local mode as well as MapReduce mode. This paper further explains in brief about the different steps required to analyze unstructured web server log files in Apache Pig. This paper also compares the efficiency when a large volume of data is processed on MapReduce mode and local mode

Definition of avionics concepts for a heavy lift cargo vehicle. Volume 1: Executive summary

A cost effective, multiuser simulation, test, and demonstration facility to support the development of avionics systems for future space vehicles is examined. The technology needs and requirements of future Heavy Lift Cargo Vehicles (HLCVs) are analyzed and serve as the basis for sizing of the avionics facility, although the lab is not limited in use to support of HLCVs. Volume 1 provides a summary of the vehicle avionics trade studies, the avionics lab objectives, a summary of the lab's functional requirements and design, physical facility considerations, and cost estimates