Rewriting of conjunctive queries using views has many applications in database and data *** investigate ways to improve performance of rewriting and propose a new algorithm which has two phases. In the first phase, si...
详细信息
Rewriting of conjunctive queries using views has many applications in database and data *** investigate ways to improve performance of rewriting and propose a new algorithm which has two phases. In the first phase, similar to Minicon, we find mapping information, which we call coverages, from subgoals in the query to subgoals in view, and assign positive integers (n) as identifiers to these coverages, where n is the number of subgoals in the query. In the rewriting phase, based on the available identifiers and partitions of the set -1, ., 2n-1}, we define patterns and use them to encode the buckets and the coverages they contain. This breaks the cartesian product of a set of large buckets into several cartesian products on sets of smaller buckets. In other words, an expensive cartesian product could be broken into a maximum of B(n) small cartesian products, where B is the Bell number. Our numerous experiments using different query types and sizes indicate significant time and space improvement for computing the cartesian products of the buckets and generating the output.
Numerous logic frameworks have been proposed for modeling uncertainty and reasoning with such data. While different in syntax, the approaches of these frameworks have been classified into "annotation based" ...
详细信息
ISBN:
(纸本)9781577354192
Numerous logic frameworks have been proposed for modeling uncertainty and reasoning with such data. While different in syntax, the approaches of these frameworks have been classified into "annotation based" (AB) and "implication based" (IB). In this paper, we present a unified framework which allows evaluating programs in either approach. It extends existing query processing techniques to handle certainty constraints and uses heuristics to further improve the performance. Our experiments indicate that the proposed techniques yield useful tools for uncertainty reasoning.
This paper describes an approach to improving the robustness of an agent system by augmenting its failure-handling capabilities. The approach is based on the concept of semantic compensation: "cleaning up" f...
详细信息
The application and development of Web technology is limited by the integrative performance of web server. Analyzed the principle of web service and the system's overloading, showed the critical parts that influen...
详细信息
Since the main objective of PCS networks is to provide "anytime- anywhere" cellular service, the existence of lost calls has become the major problem that hardly degrades the performance of such networks. A ...
详细信息
The factory of the future is the Wireless Factory - fully programmable, nimble and adaptive to planned mode changes and unplanned faults. Today automotive assembly lines loose over $22,000 per minute of downtime. The ...
详细信息
ISBN:
(纸本)9781424451081
The factory of the future is the Wireless Factory - fully programmable, nimble and adaptive to planned mode changes and unplanned faults. Today automotive assembly lines loose over $22,000 per minute of downtime. The systems are rigid, difficult to maintain, operate and diagnose. Our goal is to demonstrate the initial architecture and protocols for all-wireless factory control automation. Embedded wireless networks have largely focused on open-loop sensing and monitoring. To address actuation in closed-loop wireless control systems there is a strong need to re-think the communication architectures and protocols for reliability, coordination and control. As the links, nodes and topology of wireless systems are inherently unreliable, such time-critical and safety-critical applications require programming abstractions where the tasks are assigned to the sensors, actuators and controllers as a single component rather than statically mapping a set of tasks to a specific physical node at design time. To this end, we introduce the Embedded Virtual Machine (EVM), a powerful and flexible runtime system where virtual components and their properties are maintained across node boundaries. EVM-based algorithms introduce new capabilities such as provably minimal graceful degradation during sensor/actuator failure, adaptation to mode changes and runtime optimization of resource consumption. Through the design of a micro-factory we aim to demonstrate the capabilities of EVM-based wireless networks. Copyright 2009 ACM.
The k-anonymity technique is widely used to provide location privacy protection for accessing location-based services (LBS), i.e., the exact location of a query initiator is cloaked into a spatial region that contains...
详细信息
Comparison Shopping Agents are web applications that can help on-line shoppers to find the optimized value for commodities and/or services by parsing product descriptions. Adaption of mobile agent system, which has ca...
详细信息
Current web search engines return query-biased snippets for each document they list in a result set. For efficiency, search engines operating on large collections need to cache snippets for common queries, and to cach...
详细信息
The pervasive use of wireless networks and mobile devices has been changing our living style significantly. Along with great convenience and efficiency, there are new challenges in protecting sensitive and/or private ...
详细信息
暂无评论