3,167 research outputs found
Program Transformations for Asynchronous and Batched Query Submission
The performance of database/Web-service backed applications can be
significantly improved by asynchronous submission of queries/requests well
ahead of the point where the results are needed, so that results are likely to
have been fetched already when they are actually needed. However, manually
writing applications to exploit asynchronous query submission is tedious and
error-prone. In this paper we address the issue of automatically transforming a
program written assuming synchronous query submission, to one that exploits
asynchronous query submission. Our program transformation method is based on
data flow analysis and is framed as a set of transformation rules. Our rules
can handle query executions within loops, unlike some of the earlier work in
this area. We also present a novel approach that, at runtime, can combine
multiple asynchronous requests into batches, thereby achieving the benefits of
batching in addition to that of asynchronous submission. We have built a tool
that implements our transformation techniques on Java programs that use JDBC
calls; our tool can be extended to handle Web service calls. We have carried
out a detailed experimental study on several real-life applications, which
shows the effectiveness of the proposed rewrite techniques, both in terms of
their applicability and the performance gains achieved.Comment: 14 page
An Architecture for Provenance Systems
This document covers the logical and process architectures of provenance systems. The logical architecture identifies key roles and their interactions, whereas the process architecture discusses distribution and security. A fundamental aspect of our presentation is its technology-independent nature, which makes it reusable: the principles that are exposed in this document may be applied to different technologies
Architecture for Provenance Systems
This document covers the logical and process architectures of provenance systems. The logical architecture identifies key roles and their interactions, whereas the process architecture discusses distribution and security. A fundamental aspect of our presentation is its technology-independent nature, which makes it reusable: the principles that are exposed in this document may be applied to different technologies
Autonomous antenna tracking system for mobile symphonie ground stations
The implementation of a satellite tracking and antenna control system is described. Due to the loss of inclination control for the symphonie satellites, it became necessary to equip the parabolic antennas of the mobile Symphonie ground station with tracking facilities. For the relatively low required tracking accuracy of 0.5 dB, a low cost, step track system was selected. The step track system developed for this purpose and tested over a long period of time in 7 ground stations is based on a search step method with subsequent parabola interpolation. As compared with the real search step method, the system has the advantage of a higher pointing angle resolution, and thus a higher tracking accuracy. When the pilot signal has been switched off for a long period of time, as for instance after the eclipse, the antenna is repointed towards the satellite by an automatically initiated spiral search scan. The function and design of the tracking system are detailed, while easy handling and tracking results
Cobra: A Framework for Cost Based Rewriting of Database Applications
Database applications are typically written using a mixture of imperative
languages and declarative frameworks for data processing. Application logic
gets distributed across the declarative and imperative parts of a program.
Often, there is more than one way to implement the same program, whose
efficiency may depend on a number of parameters. In this paper, we propose a
framework that automatically generates all equivalent alternatives of a given
program using a given set of program transformations, and chooses the least
cost alternative. We use the concept of program regions as an algebraic
abstraction of a program and extend the Volcano/Cascades framework for
optimization of algebraic expressions, to optimize programs. We illustrate the
use of our framework for optimizing database applications. We show through
experimental results, that our framework has wide applicability in real world
applications and provides significant performance benefits
Tau Prolog: A Prolog interpreter for the Web
Tau Prolog is a client-side Prolog interpreter fully implemented in
JavaScript, which aims at implementing the ISO Prolog Standard. Tau Prolog has
been developed to be used with either Node.js or a browser seamlessly, and
therefore, it has been developed following a non-blocking, callback-based
approach to avoid blocking web browsers. Taking the best from JavaScript and
Prolog, Tau Prolog allows the programmer to handle browser events and
manipulate the Document Object Model (DOM) of a web using Prolog predicates. In
this paper we describe the architecture of Tau Prolog and its main packages for
interacting with the Web, and we present its programming environment. Under
consideration in Theory and Practice of Logic Programming (TPLP).Comment: 21 pages, 3 figures, under consideration in Theory and Practice of
Logic Programming (TPLP
Integrating Distributed Sources of Information for Construction Cost Estimating using Semantic Web and Semantic Web Service technologies
A construction project requires collaboration of several organizations such as owner, designer, contractor, and material supplier organizations. These organizations need to exchange information to enhance their teamwork. Understanding the information received from other organizations requires specialized human resources. Construction cost estimating is one of the processes that requires information from several sources including a building information model (BIM) created by designers, estimating assembly and work item information maintained by contractors, and construction material cost data provided by material suppliers. Currently, it is not easy to integrate the information necessary for cost estimating over the Internet. This paper discusses a new approach to construction cost estimating that uses Semantic Web technology. Semantic Web technology provides an infrastructure and a data modeling format that enables accessing, combining, and sharing information over the Internet in a machine processable format. The estimating approach presented in this paper relies on BIM, estimating knowledge, and construction material cost data expressed in a web ontology language. The approach presented in this paper makes the various sources of estimating data accessible as Simple Protocol and Resource Description Framework Query Language (SPARQL) endpoints or Semantic Web Services. We present an estimating application that integrates distributed information provided by project designers, contractors, and material suppliers for preparing cost estimates. The purpose of this paper is not to fully automate the estimating process but to streamline it by reducing human involvement in repetitive cost estimating activities
Computer systems
In addition to the discussions, Ocean Climate Data Workshop hosts gave participants an opportunity to hear about, see, and test for themselves some of the latest computer tools now available for those studying climate change and the oceans. Six speakers described computer systems and their functions. The introductory talks were followed by demonstrations to small groups of participants and some opportunities for participants to get hands-on experience. After this familiarization period, attendees were invited to return during the course of the Workshop and have one-on-one discussions and further hands-on experience with these systems. Brief summaries or abstracts of introductory presentations are addressed
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