NEC

About: NEC is a company organization based out in Tokyo, Japan. It is known for research contribution in the topics: Signal & Layer (electronics). The organization has 33269 authors who have published 57670 publications receiving 835952 citations. The organization is also known as: NEC Corporation & NEC Electronics Corporation.

Database intergration using neural networks: implementation and experiences

Abstract: Applications in a wide variety of industries require access to multiple heterogeneous distributed databases. One step in heterogeneous database integration is semantic integration: identifying corresponding attributes in different databases that represent the same real world concept. The rules of semantic integration can not be ‘pre-programmed’ since the information to be accessed is heterogeneous and attribute correspondences could be fuzzy. Manually comparing all possible pairs of attributes is an unreasonably large task. We have applied artificial neural networks (ANNs) to this problem. Metadata describing attributes is automatically extracted from a database to represent their ‘signatures’. The metadata is used to train neural networks to find similar patterns of metadata describing corresponding attributes from other databases. In our system, the rules to determine corresponding attributes are discovered through machine learning. This paper describes how we applied neural network techniques in a database integration problem and how we represent an attribute with its metadata as discriminators. This paper focuses on our experiments on effectiveness of neural networks and each discriminator. We also discuss difficulties of using neural networks for this problem and our wish list for the Machine Learning community.

Methods for Sampling Pages Uniformly from the World Wide Web

Abstract: We present two new algorithms for generating uniformly random samples of pages from the World Wide Web, building upon recent work by Henzinger et al. (Henzinger et al. 2000) and Bar-Yossef et al. (Bar-Yossef et al. 2000). Both algorithms are based on a weighted random-walk methodology. The first algorithm (DIRECTED-SAMPLE) operates on arbitrary directed graphs, and so is naturally applicable to the web. We show that, in the limit, this algorithm generates samples that are uniformly random. The second algorithm (UNDIRECTED-SAMPLE) operates on undirected graphs, thus requiring a mechanism for obtaining inbound links to web pages (e.g., access to a search engine). With this additional knowledge of inbound links, the algorithm can arrive at a uniform distribution faster than DIRECTEDSAMPLE, and we derive explicit bounds on the time to convergence. In addition, we evaluate the two algorithms on simulated web data, showing that both yield reliably uniform samples of pages. We also compare our results with those of previous algorithms, and discuss the theoretical relationships among the various proposed methods.

Partition-based decision heuristics for image computation using SAT and BDDs

Abstract: Methods based on Boolean satisfiability (SAT) typically use a Conjunctive Normal Form (CNF) representation of the Boolean formula, and exploit the structure of the given problem through use of various decision heuristics and implication methods. In this paper, we propose a new decision heuristic based on separator-set induced partitioning of the underlying CNF graph. It targets those variables whose choice generates clause partitions with disjoint variable supports. This can potentially improve performance of SAT applications by decomposing the problem dynamically within the search. In the context of a recently proposed image computation method combining SAT and BDDs, this results in simpler BDD subproblems. We provide algorithms for CNF partitioning -- one based on a clause-variable dependency matrix, and another based on standard hypergraph partitioning techniques, and also for the use of partitioning information in decision heuristics for SAT. We demonstrate the effectiveness of our proposed partition-based heuristic with practical results for reachability analysis of benchmark sequential circuits.

Securing wireless data: system architecture challenges

Abstract: Security is critical to a wide range of current and future wireless data applications and services. This paper highlights the challenges posed by the need for security during system architecture design for wireless handsets, and provides an overview of emerging techniques to address them. We focus on the computational requirements for securing wireless data transactions, revealing a gap between these requirements and the trends in processing capabilities of embedded processors used in wireless handsets. We also demonstrate that the use of security protocols causes significant degradation in battery life, a problem that will worsen due to the slow growth in battery capacities. These trends point to a wireless security processing gap that, unless addressed, will impede the deployment of secure high-speed wireless data and multi-media applications. We discuss approaches that are currently being pursued to bridge this gap, including low-complexity cryptographic algorithms, security enhancements to embedded processors, and advanced system architectures for wireless handsets that are enabled by new system level design methodologies.

Shared cache server

Abstract: A shared cache server which is capable of being shared among groups in a common network in which a plurality of groups is placed in a virtually partitioned manner A storage device stores contents in each of a plurality of storage areas corresponding to a plurality of groups Virtual interfaces are placed in a manner so as to correspond to a plurality of virtual networks An address converting function section, when receiving a packet requiring for contents through the virtual interface from a client, converts part of an IP (Internet Protocol) of the packet to an internal address corresponding to the virtual interface A cache function section, based on the internal address converted by the address converting function section, reads contents of a corresponding group from a storage area of the storage device