281,582 research outputs found
Performance analysis of a real-time database with optimistic concurrency control
For a real-time shared-memory database with Optimistic Concurrency Control (OCC), an approximation for the transaction response-time distribution and thus for the deadline miss probability is obtained. Transactions arrive at the database according to a Poisson process. There is a limited number of CPUs that can handle transactions in parallel. TransactIons have soft deadlines, and the probability of data conflicts is equal for all transactions. The response time of a transaction consists of possible waiting time (if at arrival all CPUs are occupied) plus a number of execution runs (due to the occurrence of conflicts). In this study, we analyze the case where the execution time of all transactions is constant. Although in practice execution times are never really constant, it is important to analyze this simplifying constant case first, before trying to analyze more general execution-time distributions. We model the real-time database (RTDB) with OCC by a multi-server queueing system with a very special kind of feedback. The probability that a transaction is fed back for a rerun depends on the number of transactions that has committed during its execution. Numerical experiments, which compare the approximative analysis with simulation, show that the analysis provides a good and very fast approximation for the response-time distribution and thus for the percentage of transactions that meets its deadline. We also discuss how the model and the analysis can be extended such that more realistic assumptions, e.g. non-uniform data access, several transaction types, and general execution-time distributions, can be handled
Uniform: The Form Validation Language
Digital forms are becoming increasingly more prevalent but the ease of creation is not. Web Forms are difficult to produce and validate. This design project seeks to simplify this process. This project is comprised of two parts: a logical programming language (Uniform) and a web application.
Uniform is a language that allows its users to define logical relationships between web elements and apply simple rules to individual inputs to both validate the form and manipulate its components depending on user input. Uniform provides an extra layer of abstraction to complex coding.
The web app implements Uniform to provide business-level programmers with an interface to build and manage forms. Users will create form templates, manage form instances, and cooperatively complete forms through the web app.
Uniform’s development is ongoing, it will receive continued support and is available as open-source. The web application is software owned and maintained by HP Inc. which will be developed further before going to market
Youth Gang Violence and Guns: Data Collection in California
Provides an overview of data on youth gang-related homicides, the role of firearms in the rising lethality of gang violence, and the state of data collection. Illustrates the need for a comprehensive database to support effective prevention policies
What Can We Learn Privately?
Learning problems form an important category of computational tasks that
generalizes many of the computations researchers apply to large real-life data
sets. We ask: what concept classes can be learned privately, namely, by an
algorithm whose output does not depend too heavily on any one input or specific
training example? More precisely, we investigate learning algorithms that
satisfy differential privacy, a notion that provides strong confidentiality
guarantees in contexts where aggregate information is released about a database
containing sensitive information about individuals. We demonstrate that,
ignoring computational constraints, it is possible to privately agnostically
learn any concept class using a sample size approximately logarithmic in the
cardinality of the concept class. Therefore, almost anything learnable is
learnable privately: specifically, if a concept class is learnable by a
(non-private) algorithm with polynomial sample complexity and output size, then
it can be learned privately using a polynomial number of samples. We also
present a computationally efficient private PAC learner for the class of parity
functions. Local (or randomized response) algorithms are a practical class of
private algorithms that have received extensive investigation. We provide a
precise characterization of local private learning algorithms. We show that a
concept class is learnable by a local algorithm if and only if it is learnable
in the statistical query (SQ) model. Finally, we present a separation between
the power of interactive and noninteractive local learning algorithms.Comment: 35 pages, 2 figure
Efficient Management of Short-Lived Data
Motivated by the increasing prominence of loosely-coupled systems, such as
mobile and sensor networks, which are characterised by intermittent
connectivity and volatile data, we study the tagging of data with so-called
expiration times. More specifically, when data are inserted into a database,
they may be tagged with time values indicating when they expire, i.e., when
they are regarded as stale or invalid and thus are no longer considered part of
the database. In a number of applications, expiration times are known and can
be assigned at insertion time. We present data structures and algorithms for
online management of data tagged with expiration times. The algorithms are
based on fully functional, persistent treaps, which are a combination of binary
search trees with respect to a primary attribute and heaps with respect to a
secondary attribute. The primary attribute implements primary keys, and the
secondary attribute stores expiration times in a minimum heap, thus keeping a
priority queue of tuples to expire. A detailed and comprehensive experimental
study demonstrates the well-behavedness and scalability of the approach as well
as its efficiency with respect to a number of competitors.Comment: switched to TimeCenter latex styl
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
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