15030712
Impact of mobility on transaction management
We examine the impact of mobility on three different options to managing mobile transactions. Using an analytic performance study we show that no one management approach is always the best and that the performance is impacted by the location management strategy used. The primary objective of this work is to illustrate that the underlying implementation strategies do indeed impact mobile transaction processing and should be considered when proposing mobile transaction processing techniques.
16958826
Recent Advances and Research Problems in Data Warehousing
In the recent years, the database community has witnessed the emergence of a new technology, namely data warehousing. A data warehouse is a global repository that stores pre-processed queries on data which resides in multiple, possibly heterogeneous, operational or legacy sources. The information stored in the data warehouse can be easily and efficiently accessed for making effective decisions. The On-Line Analytical Processing (OLAP) tools access data from the data warehouse for complex data analysis, such as multidimensional data analysis, and decision support activities. Current research has lead to new developments in all aspects of data warehousing, however, there are still a number of problems that need to be solved for making data warehousing effective. In this paper, we discuss recent developments in data warehouse modelling, view maintenance, and parallel query processing. A number of technical issues for exploratory research are presented and possible solutions are discussed.
35078097
An adaptive location management algorithm for mobile computing
In mobile computing mobile hosts or mobile units move randomly from one place to another within a well-defined geographical area. This requires some mechanism for identifying the exact location of a mobile host. Such mechanisms are usually referred to as location management and is one of the essential components for supporting mobility. In the past a number of efficient location management schemes have been suggested but they lack adaptability. We believe that an adaptable location management scheme is more desirable because of frequent change in the location of mobile hosts. In this paper, we report a location management algorithm, which adapts to the constant changing scenario. Our algorithm makes use of some of the concepts of location management schemes proposed in the past.
34436430
An Integrated Data Structure with Multiple Access Paths for Database Systems and its Performance
Abstract In the past a number of file organizations have been proposed for processing different types of queries efficiently. To our knowledge none of the existing file organizations is capable of supporting all types of accesses equally efficiently. In this paper we have taken a different approach for designing an integated data structure which offers multiple access paths for processing different types of queries efficiently. The data structure reported here can be implemented on disk based as well as main memory database systems, however, in this paper we report its behavior mainly in main memory database environment. Our approach is to fuse those data structures which offer an efficient access paths for a particular type. To show the feasibility of our scheme we fused the B+-tree, the grid file and extendible hashing structures, using a proper interface. We implemented and measured its performance through simulation modeling. Our results show that the data structure does improve concurrency and offers a higher throughput for a variety of transaction processing workloads. We argue that our scheme is different than creating secondary indexes for improving concurrency. In the absence of a data strucure which can provide all types of access equally efficiently, an integrated data structure is an acceptable solution which offers an efficient way for increasing the performance of database management systems.
29393244
Semantic Caching and Query Processing
Semantic caching is very attractive for use in distributed systems due to the reduced network traffic and the improved response time. It is particularly efficient for a mobile computing environment, where the bandwidth of wireless links is a major performance bottleneck. Previous work either does not provide a formal semantic caching model, or lacks efficient query processing strategies. This paper extends the existing research in three ways: formal definitions associated with semantic caching are presented, query processing strategies are investigated and, finally, the performance of the semantic cache model is examined through a detailed simulation study.
8261257
TCOT-A Timeout-Based Mobile Transaction Commitment Protocol
We present a transaction commit protocol, "Transaction Commit On Timeout (TCOT)," based on a "timeout" approach for Mobile Database Systems (MDS), which can be universally used to reach a final transaction termination decision (e.g., commit, abort, etc.) in any message-oriented system. Particularly suited for a wireless environment, a timeout mechanism is the only way to minimize the impact of the slow and unreliable wireless link. We compare TCOT to a modified version of 2PC to show its superiority based on commit time.
14506171
Optimal constrained graph exploration
We address the problem of exploring an unknown graph <i>G</i> = (<i>V</i>, <i>E</i>) from a given start node <i>s</i> with either a tethered robot or a robot with a fuel tank of limited capacity, the former being a tighter constraint. In both variations of the problem, the robot can only move along the edges of the graph, i.e, it cannot jump between non-adjacent vertices. In the tethered robot case, if the tether (rope) has length <i>l</i>, then the robot must remain within distance <i>l</i> from the start node <i>s</i>. In the second variation, a fuel tank of limited capacity forces the robot to return to <i>s</i> after traversing <i>C</i> edges. The efficiency of algorithms for both variations of the problem is measured by the number of edges traversed during the exploration. We present an algorithm for a tethered robot which explores the graph in <i>&Ogr;</i>(¦<i>E</i>¦) edge traversals. The problem of exploration using a robot with a limited fuel tank capacity can be solved with a simple reduction from the tethered robot case and also yields a <i>&Ogr;</i>(¦<i>E</i>¦) algorithm. This improves on the previous best known bound of <i>&Ogr;</i>(¦<i>E</i>¦ + ¦<i>V</i>¦log <sup>2</sup>¦<i>V</i>¦) in [4]. Since the lower bound for the graph exploration problems is ¦<i>E</i>¦, our algorithm is optimal, thus answering the open problem of Awerbuch, Betke, Rivest, and Singh [3].
4677633
A Strategic Modeling Technique for Change Management in Organizations Undergoing BPR
Modern day organizations seek to rationalize, innovate, and adapt to changing environments, and circumstances as part of Business Process Reengineering (BPR) efforts. Irrespective of the process reengineering program selected, and the technique used to model, BPR brings with it the issues of organizational, and process changes, which involves managing organizational changes (also called “change management”). Change management is non-trivial, as organizational changes are difficult to accomplish. Though some attempt has been made to model change management in enterprise information systems using conventional conceptual modeling techniques, they have just addressed “what” a change process is like, and they don’t address “why” the process is the way it is. Our approach is novel in the sense that it presents an actor-dependency-based 5-phased technique for analyzing, and modeling early-phase requirements of change management that provides the motivations, intents, and rationales behind activities.
11162423
Optimal Gait Selection for Nonholonomic Locomotion Systems
This paper addresses the optimal control and selection of gaits in a class of nonholonomic locomotion systems that exhibit group symmetries. We study optimal gaits for the snakeboard, a representative example of this class of systems. We employ Lagrangian reduction techniques to simplify the optimal control problem and describe a general framework and an algorithm to obtain numerical solutions to this problem. This work employs optimal control techniques to study the optimality of gaits and issues involving gait transitions. The general framework provided in this paper can easily be applied to other examples of biological and robotic locomotion.
1926044
Real-time vision-based control of a nonholonomic mobile robot
This paper considers the problem of vision-based control of a nonholonomic mobile robot. We describe the design and implementation of real-time estimation and control algorithms on a car-like robot platform using a single omni-directional camera as a sensor without explicit use of odometry. We provide experimental results for each of these vision-based control objects. The algorithms are packaged as control modes and can be combined hierarchically to perform higher level tasks involving multiple robots.
11502954
Motion generation for formations of robots: A geometric approach
Develops a method for generating smooth trajectories for mobile robots in formation. The problem of trajectory generation is cast in terms of designing optimal curves on the Euclidean group, SE(3). Specifically, the method generates the trajectory that minimizes the total energy associated with the translations and rotations of the robots, while maintaining a rigid formation. When the mobile robots are nonholonomic, trajectories that allow rigid formations to be maintained must satisfy appropriate constraints. An efficient non-iterative algorithm to obtain near-optimal trajectories is described. Finally, the approach is illustrated with examples involving formations of aircrafts.