6106969
Service-Based Distributed Querying on the Grid
Service-based approaches (such as Web Services and the Open Grid Services Architecture) have gained considerable attention recently for supporting distributed application development in e-business and e-science. The emergence of a service-oriented view of hardware and software resources raises the question as to how database management systems and technologies can best be deployed or adapted for use in such an environment. This paper explores one aspect of service-based computing and data management, viz., how to integrate query processing technology with a service-based Grid. The paper describes in detail the design and implementation of a service-based distributed query processor for the Grid. The query processor is service-based in two orthogonal senses: firstly, it supports querying over data storage and analysis resources that are made available as services, and, secondly, its internal architecture factors out as services the functionalities related to the construction of distributed query plans on the one hand, and to their execution over the Grid on the other. The resulting system both provides a declarative approach to service orchestration in the Grid, and demonstrates how query processing can benefit from dynamic access to computational resources on the Grid.
15945659
Distributed Query Processing on the Grid
Distributed query processing (DQP) has been widely used in data intensive applications where data of relevance to users is stored in multiple locations. This paper argues: (i) that DQP can be important in the Grid, as a means of providing high-level, declarative languages for integrating data access and analysis; and (ii) that the Grid provides resource management facilities that are useful to developers of DQP systems. As well as discussing and illustrating how DQP technologies can be deployed within the Grid, the paper describes a prototype implementation of a DQP system running over Globus.
13121681
A parallel algebra for object databases
The paper describes an algebra for use with parallel object databases, and in particular ODMG compliant databases with OQL. Although there have been many proposals for parallel relational database systems, there has been much less work on parallel object databases, and on parallel query processing for object databases. The parallel algebra presented in the paper is an extension of an existing physical algebra for OQL, and has an important role during query optimization, and for describing execution plans. The paper presents not only the algebra, but also its role in the architecture of a parallel database.
8773742
On Synchronisation in Fault-Tolerant Data and Compute Intensive Programs over a Network of Workstations
An application structured as a fault-tolerant bag of tasks adapts easily to changing resources. To be represented by a single bag of tasks, a computation must decompose into purely independent tasks. The work summarised here investigates performance of structuring approaches applicable where this ideal is not possible, partly through analysis and partly through measurements of a realistic fault-tolerant computation.
16226748
Polar: an architecture for a parallel ODMG compliant object database
Object database management systems (ODBMS) are now established as the database management technology of choice for a range of challenging data intensiv e applications. Furthermore, the applications associated with object databases typically have stringen t performance requirements, and some are associated with very large data sets. Ho w ever, despite the demands made on object databases by applications, there has been surprisingly little work on parallel object databases. This paper presents the arc hitecture and some preliminary performance results for the Polar ODMG compliant parallel object database. The architecture described has been implemented in a shared-nothing environment on a network of PCs. The paper describes how OQL queries are compiled, parallelized and executed in this environment, and includes some preliminary performance results for OQL queries using the 007 benchmark.
16693115
An Experimental Performance Evaluation of Join Algorithms for Parallel Object Databases
Parallel relational databases have been successful in providing scalable performance for data intensive applications, and much work has been carried out on query processing techniques in such systems. However, although many applications associated with object databases also have stringent performance requirements, there has been much less work investigating parallel object database systems. An important feature for the performance of object databases is the speed at which relationships can be explored. In queries, this depends upon the effectiveness of different join algorithms into which queries that follow relationships can be compiled. This paper presents the results of empirical evaluations of four parallel join algorithms, two value based and two pointer based. The experiments have been run on Polar, a parallel ODMG object database system.
17602182
Architecture of the artifact-based collaboration system matrix
The UNC Collaboratory project is concerned with both the process of collaboration and with computer systems to support that process. Here, we describe a component of the Artifact-Based Collaboration (ABC) system, called the Matrix, that provides an infrastructure in which existing single-user applications can be incorporated with few, if any, changes and used collaboratively. We take the position that what is needed is not new tools but better infrastructure for using familiar single-user tools collectively. The paper discusses the Matrix architecture, a Virtual Screen component, and generic functions that provide conferencing, hyperlinking, and recording of users' actions for all applications. INTRODUCTION AND MOTIVATION
9694445
The architecture and implementation of a distributed hypermedia storage system
Our project is studying the process by which groups of individuals work together to build large, complex structures of ideas and is developing a distributed hypermedia collaboration environment (called ABC) to support that process. This paper focuses on the architecture and implementation of the Distributed Graph Storage (DGS) component of ABC. The DGS supports a graph-based data model, conservatively extended to meet hypermedia requirements. Some important issues addressed in the system include scale, performance, concurrency semantics, access protection, location independence, and replication (for fault tolerance).
16792950
Task-structure analysis for knowledge modeling
n recent years there has been increasing interest in describing complicated information processing systems in terms of the knowledge they have, rather than by the details of their implementation. This requires a means of modeling the knowledge in a system. Several different approaches to knowledge modeling have been developed by researchers working in Artificial Intelligence (AI). Most of these approaches share the view that knowledge must be modeled with respect to a goal or task. In this article , we outline our modeling approach in terms of the notion of a task-structure, which recursively links a task to alternative methods and to their subtasks. Our emphasis is on the notion of modeling domain knowledge using tasks and methods as mediating concepts. We begin by tracing the development of a number of different knowledge-modeling approaches. These approaches share many features, but their differences make it difficult to compare systems that have been modeled using different approaches. We present these approaches and describe their similarities and differences. We then give a detailed description , based on the task structure, of our knowledge-modeling approach and illustrate it with task structures for diagnosis and design. Finally, we show how the task structure can be used to compare and unify the other approaches. A knowledge-based system (KBS) has explicit representations of knowledge as well as inference processes that operate on these representations to achieve a goal. An inference process consists of a number of inference steps, each step creating additional knowledge. The process of applying inference steps is repeated until the information needed to fulfill the requirements of the problem-solving goal or task is generated. Typically, both domain knowledge and possible inference steps have to be modeled and represented in some form. In one sense, knowledge is of general utility-the same piece can be utilized in different contexts and problems; so, unlike traditional procedural approaches, knowledge should not be tied to one task or goal. On the other hand, it is difficult to know what knowledge to put in a system without having an idea of the tasks the KBS will confront. In spite of claims of generality, all KBSs are designed with some task or class of tasks in mind. Similarly, they are designed to be operational across some range of domains. Thus, a clear understanding of the relationship between tasks, knowledge and inferences required to perform the task is needed before knowledge in …
37291538
The Ensembl genome database project
The Ensembl (http://www.ensembl.org/) database project provides a bioinformatics framework to organise biology around the sequences of large genomes. It is a comprehensive source of stable automatic annotation of the human genome sequence, with confirmed gene predictions that have been integrated with external data sources, and is available as either an interactive web site or as flat files. It is also an open source software engineering project to develop a portable system able to handle very large genomes and associated requirements from sequence analysis to data storage and visualisation. The Ensembl site is one of the leading sources of human genome sequence annotation and provided much of the analysis for publication by the international human genome project of the draft genome. The Ensembl system is being installed around the world in both companies and academic sites on machines ranging from supercomputers to laptops.
5116030
Automated Recovery in a Secure Bootstrap Process
Integrity is rarely a valid presupposition in many systems architectures, yet it is necessary to make any security guarantees. To address this problem, we have designed a secure bootstrap process, AEGIS, which presumes a minimal amount of integrity, and which we have prototyped on the Intel x86 architecture. The basic principle is sequencing the bootstrap process as a chain of progressively higher levels of abstraction, and requiring each layer to check a digital signature of the next layer before control is passed to it. A major design decision is the consequence of a failed integrity check. A simplistic strategy is to simply halt the bootstrap process. However, as we show in this paper, the AEGIS bootstrap process can be augmented with automated recovery procedures which preserve the security properties of AEGIS under the additional assumption of the availability of a trusted repository. We describe two means by which such a repository can be implemented, and focus our attention on a network-accessible repository.