A federated database system (FDBS) is a collection of cooperating database systems that are autonomous and possibly heterogeneous. In this paper, we define a reference architecture for distributed database management systems from system and schema viewpoints and show how various FDBS architectures can be developed. We then define a methodology for developing one of the popular architectures of an FDBS. Finally, we discuss critical issues related to developing and operating an FDBS.

Federated database systems for managing distributed, heterogeneous, and autonomous databases

We discuss the design of an acquisitional query processor for data collection in sensor networks. Acquisitional issues are those that pertain to where, when, and how often data is physically acquired (sampled) and delivered to query processing operators. By focusing on the locations and costs of acquiring data, we are able to significantly reduce power consumption over traditional passive systems that assume the a priori existence of data. We discuss simple extensions to SQL for controlling data acquisition, and show how acquisitional issues influence query optimization, dissemination, and execution. We evaluate these issues in the context of TinyDB, a distributed query processor for smart sensor devices, and show how acquisitional techniques can provide significant reductions in power consumption on our sensor devices.

/pdf/tinydb-an-acquisitional-query-processing-system-for-sensor-2akih312yn.pdf

TinyDB: an acquisitional query processing system for sensor networks

An adaptive interface for a programmable system, for predicting a desired user function, based on user history, as well as machine internal status and context. The apparatus receives an input from the user and other data. A predicted input is presented for confirmation by the user, and the predictive mechanism is updated based on this feedback. Also provided is a pattern recognition system for a multimedia device, wherein a user input is matched to a video stream on a conceptual basis, allowing inexact programming of a multimedia device. The system analyzes a data stream for correspondence with a data pattern for processing and storage. The data stream is subjected to adaptive pattern recognition to extract features of interest to provide a highly compressed representation which may be efficiently processed to determine correspondence. Applications of the interface and system include a VCR, medical device, vehicle control system, audio device, environmental control system, securities trading terminal, and smart house. The system optionally includes an actuator for effecting the environment of operation, allowing closed-loop feedback operation and automated learning.

Ergonomic man-machine interface incorporating adaptive pattern recognition based control system

b this paper we present a case for using new power-aware metn.cs for determining routes in wireless ad hoc networks. We present five ~erent metriw based on battery power consumption at nodw. We show that using th=e metrics in a shortest-cost routing algorithm reduces the cost/packet of routing packets by 5-30% over shortwt-hop routing (this cost reduction is on top of a 40-70% reduction in energy consumption obtained by using PAMAS, our MAC layer prtocol). Furthermore, using these new metrics ensures that the mean time to node failure is increased si~cantly. An interesting property of using shortest-cost routing is that packet delays do not increase. Fintiy, we note that our new metrim can be used in most tradition routing protocols for ad hoc networks.

/pdf/power-aware-routing-in-mobile-ad-hoc-networks-44xb4c3yoo.pdf

Power-aware routing in mobile ad hoc networks

In this paper we develop a new multiaccess protocol for ad hoc radio networks. The protocol is based on the original MACA protocol with the adition of a separate signalling channel. The unique feature of our protocol is that it conserves battery power at nodes by intelligently powering off nodes that are not actively transmitting or receiving packets. The manner in which nodes power themselves off does not influence the delay or throughput characteristics of our protocol. We illustrate the power conserving behavior of PAMAS via extensive simulations performed over ad hoc networks containing 10-20 nodes. Our results indicate that power savings of between 10% and 70% are attainable in most systems. Finally, we discuss how the idea of power awareness can be built into other multiaccess protocols as well.

PAMAS—power aware multi-access protocol with signalling for ad hoc networks

This paper proposes the use of repetitive broadcast as a way of augmenting the memory hierarchy of clients in an asymmetric communication environment. We describe a new technique called "Broadcast Disks" for structuring the broadcast in a way that provides improved performance for non-uniformly accessed data. The Broadcast Disk superimposes multiple disks spinning at different speeds on a single broadcast channel--in effect creating an arbitrarily fine-grained memory hierarchy. In addition to proposing and defining the mechanism, a main result of this work is that exploiting the potential of the broadcast structure requires a re-evaluation of basic cache management policies. We examine several "pure" cache management policies and develop and measure implementable approximations to these policies. These results and others are presented in a set of simulation studies that substantiates the basic idea and develops some of the intuitions required to design a particular broadcast program.

/pdf/broadcast-disks-data-management-for-asymmetric-communication-2ws2o1c7w5.pdf

Broadcast disks: data management for asymmetric communication environments

Broadcast Disks: Data Management for Asymmetric Communication Environments.

Thi s pape r proposes th e use of repetitiv e broadcas t as a way of augmentin g th e mem ­ ory hierarchy of clients in an asymmetri c communicatio n environment . We describe a ne w techniqu e called "Broadcas t Disks" for structurin g th e broadcas t in a way tha t provides improve d performanc e for non-uniformly accessed data . Th e Broadcas t Disk superimpose s multipl e disks spinnin g at different speeds on a single broadcas t chan­ nel — in effect creatin g an arbitraril y fine-grained memor y hierarchy. In additio n to proposin g an d defining th e mechanism , a mai n result of thi s work is tha t exploiting th e potentia l of th e broadcas t structur e requires a re-evaluation of basic cache man ­ agemen t policies. We examin e several "pure " cache managemen t policies an d develop Previously appeared in Proceedings of the ACM SIGMOD International Conference on the Management of Data, 1995, pp. 199-210. Copyright ©1995 by the Association for Com­ puting Machinery, Inc. Reprinted by permission. Permission to make digital or hard copies of part or all of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or direct commercial advantage and that copies bear this notice and the full citation on the first page. Copyrights for components of this work owned by others than ACM must be honored. Abstracting with credit is permitted. To copy otherwise, to republish, to post on servers, or to redistribute to lists, requires prior specific permission and/or a fee. Request permissions from Publications Dept, ACM Inc., fax +1 (212) 869-0481,or (permissions@acm.org)

Broadcast Disks: Data Management for Asymmetric Communications Environments.

Currently, a variety of information retrieval systems are available to potential users.… While in many cases these systems are accessed from personal computers, typically no advantage is taken of the computing resources of those machines (such as local processing and storage). In this paper we explore the possibility of using the user's local storage capabilities to cache data at the user's site. This would improve the response time of user queries albeit at the cost of incurring the overhead required in maintaining multiple copies. In order to reduce this overhead it may be appropriate to allow copies to diverge in a controlled fashion.… Thus, we introduce the notion of quasi-copies, which embodies the ideas sketched above. We also define the types of deviations that seem useful, and discuss the available implementation strategies.—From the Authors' Abstract

/pdf/data-caching-issues-in-an-information-retrieval-system-2mfxoa3vn6.pdf

Data caching issues in an information retrieval system

In this paper, we present Bit-Sequences (BS), an adaptive cache invalidation algorithm for client/server mobile environments. The algorithm uses adaptable mechanisms to adjust the size of the invalidation report to optimize the use of a limited communication bandwidth while retaining the effectiveness of cache invalidation. The proposed BS algorithm is especially suited for dissemination-based (or “server-push”-based) nomadic information service applications. The critical aspect of our algorithm is its self-adaptability and effectiveness, regardless of the connectivity behavior of the mobile clients. The performance of BS is analyzed through a simulation study that compares BS's effectiveness with that of a hypothetical optimal cache invalidation algorithm.

http://delab.csd.auth.gr/~dimitris/courses/mpc_fall05/proj_papers/ACM_MONET_97_Bit_Sequences.pdf

Rafael Alonso

Papers

Broadcast disks: data management for asymmetric communication environments

Broadcast Disks: Data Management for Asymmetric Communication Environments.

Broadcast Disks: Data Management for Asymmetric Communications Environments.

Data caching issues in an information retrieval system

Bit-sequences: an adaptive cache invalidation method in mobile client/server environments