15093463
Arithmetic for Parallel Linear Recursive Query Evaluation in Deductive Databases
An arithmetic approach, such as the Level-Finding method described in this paper for evaluating linear recursive queries in deductive database systems provides great potential for parallel processing. It has advantages over other approaches using state-of-the-art parallel processing technology to improve processing speed. In the arithmetic approach, we identify two kind of parallelism, namely bridge node parallelism and formula parallelism. In this paper, the arithmetic foundations and algorithm to exploit formula parallelism were given. The algorithm is fully parallel.
12408680
Utilising Multiple Computers in Database Query Processing and Descriptor Rule Management
A fundamental problem to be solved in systems that derive rules from database tables to use in query optimisation is the workload involved. If the data server has to do the work it can interfere with query processing and cause slower query answering, which is the opposite of the required effect. This paper reports our investigation of the use of multiple workstations in the same local network as the data server to derive and maintain sets of rules describing data subsets. These rules are used in query optimisation. In a local area network of workstations, one computer accepts SQL queries and data manipulation commands from networked clients. This computer provides an interface to one or more database management systems located on computers in the network. It uses a collection of subset-descriptor rules for query reformulation before forwarding the semantically optimised query. It manages a set of workstations in the network, to derive and maintain the rules. The workstations are ordinary networked computers whose spare computing capacity is utilised by spawning background programs on them.
11146897
Constructing Inter-relational Rules for Semantic Query Optimisation
Semantic query optimisation is the process by which a user query is transformed into a set of alternative queries each of which returns the same answer as the original. The most efficient of these alternatives is then selected, for execution, using standard cost estimation techniques. The query transformation process is based on the use of semantic knowledge in the form of rules which are generated either during the query process itself or are constructed according to defined heuristics. Previous research has tended to focus on constructing rules applicable to single relations and does not take advantage of the additional semantic knowledge, inherent in most databases, associated with relational joins. Our paper seeks to address this weakness by showing how the rule derivation process may be extended to the generation of inter-relational rules using an approach based on inductive learning.
10379830
Extended Query Answering Using Integrity Rules
The conventional use of databases is commonly restricted to the retrieval of factual data in the form of tuples or records. However most databases also contain metadata in the form of integrity rules which can provide a rich source of additional information not normally available to the user. Integrity rules define what data values and relationships may exist within the database and so their interrogation can provide answers as to whether a certain database state is possible. Our paper describes how this may be achieved and specifies a formal approach to implementing such an enquiry system.
6479052
Data Analysis for Query Processing
Data analysis is needed in connection with query processing, to produce data summary information in the form of rules or assertions that allow semantic query optimisation or direct query answering without consulting the data itself. The goal of an intelligent analyser in this context is to produce robust rules, stable in the presence of data changes, which allow easy rule maintenance as data changes, and provide rapid query reformulation, refutation or answering. It must also limit the rule set to rules useful for query processing.
14933774
Using a Network of Workstations to Enhance Database Query Processing Performance
Query processing in database systems may be improved by applying parallel processing techniques. One reason for improving query response time is to support the increased number queries when databases are made accessible from the Internet.
40861592
Definability and Decision Problems in Arithmetic
In this paper, we are concerned with the arithmetical definability of certain notions of integers and rationals in terms of other notions. The results derived will be applied to obtain a negative solution of corresponding decision problems. In Section 1, we show that addition of positive integers can be defined arithmetically in terms of multiplication and the unary operation of successor S (where Sa = a + 1). Also, it is shown that both addition and multiplication can be defined arithmetically in terms of successor and the relation of divisibility | (where x|y means x divides y ).
17448440
Effective implementation of cycle time reduction strategies for semiconductor back-end manufacturing
Using discrete event simulation models, a study was conducted to evaluate the current production practices of a high volume semiconductor back-end operation. The overall goal was to find potential areas for productivity improvement that would collectively yield a 60% reduction in manufacturing cycle time. The paper presents the simulation methodology and findings pertaining to analysis of the Assembly, Burn-In, and Test operations. Many of the recommendations identified can be implemented at no additional cost to the factory. The most significant opportunities for improvement are in the Test area, the system constraint. Additionally, the model is extremely sensitive to changes in operator staffing levels, an accurate reflection of many back-end operations. The model shows that the cumulative impact of these recommendations is a 41% reduction in average cycle time, a significant contribution to the overall goal.
12209685
Measurement driven deployment of a two-tier urban mesh access network
Multihop wireless mesh networks can provide Internet access over a wide area with minimal infrastructure expenditure. In this work, we present a measurement driven deployment strategy and a data-driven model to study the impact of design and topology decisions on network-wide performance and cost. We perform extensive measurements in a two-tier urban scenario to characterize the propagation environment and correlate received signal strength with application layer throughput. We find that well-known estimates for pathloss produce either heavily overprovisioned networks resulting in an order of magnitude increase in cost for high pathloss estimates or completely disconnected networks for low pathloss estimates. Modeling throughput with wireless interface manufacturer specifications similarly results in severely underprovisioned networks. Further, we measure competing, multihop flow traffic matrices to empirically define achievable throughputs of fully backlogged, rate limited, and web-emulated traffic. We find that while fully backlogged flows produce starving nodes, rate-controlling flows to a fixed value yields fairness and high aggregate throughput. Likewise, transmission gaps occurring in statistically multiplexed web traffic, even under high offered load, remove starvation and yield high performance. In comparison, we find that well-known noncompeting flow models for mesh networks over-estimate network-wide throughput by a factor of 2. Finally, our placement study shows that a regular grid topology achieves up to 50 percent greater throughput than random node placement.
6721869
A Performance Study of Deployment Factors in Wireless Mesh Networks
We present a measurement-parameterized performance study of deployment factors in wireless mesh networks using three performance metrics: client coverage area, backhaul tier connectivity, and fair mesh capacity. For each metric, we identify and study topology factors and architectural features which strongly influence mesh performance via an extensive set of Monte Carlo simulations capturing realistic physical layer behavior. Our findings include: (i) A random topology is unsuitable for a large-scale mesh deployment due to doubled node density requirements, yet a moderate level of perturbations from ideal grid placement has a minor impact on performance. (ii) Multiple backhaul radios per mesh node is a cost-effective deployment strategy as it leads to mesh deployments costing 50% less than with a single-radio architecture, (iii) Dividing access and backhaul connections onto two separate radios does not use the second radio efficiently as it only improves fair mesh capacity 40% to 80% for most users. This is in contrast to using the second radio to move half the user population to a new network operated on the second radio. This work adds to the understanding of mesh deployment factors and their general impact on performance, providing further insight into practical mesh deployments.
15957762
Sensor networks and grid middleware for laboratory monitoring
By combining automatic environment sensing and experimental data collection with broker based messaging middleware, a system has been produced far the real-time monitoring of experiments whilst away from the lab. Changes in the laboratory environment are encapsulated as simple messages, which are published using an MQTT compliant broker. Clients subscribe to the MQTT stream, and perform a data transform on the messages; this may be to produce a user display or to change the format of the message for republishing. For example, an MQTT client written for the Java MIDP platform can be run on a smart-phone with a GPRS Internet connection, freeing us from the constraints of the network. We present an overview of the technologies used, and how these are helping chemists make the best use of their time