Physical Sciences and Mathematics Commons^™

Checkpointing And Recovery In Distributed And Database Systems, Jiang Wu

Theses and Dissertations--Computer Science

A transaction-consistent global checkpoint of a database records a state of the database which reflects the effect of only completed transactions and not the re- sults of any partially executed transactions. This thesis establishes the necessary and sufficient conditions for a checkpoint of a data item (or the checkpoints of a set of data items) to be part of a transaction-consistent global checkpoint of the database. This result would be useful for constructing transaction-consistent global checkpoints incrementally from the checkpoints of each individual data item of a database. By applying this condition, we can start from any useful checkpoint of …

An Empirical Study On User Acceptance Of Simulation Techniques For Business Process, Olurotimi Adeboye Ladeinde

Walden Dissertations and Doctoral Studies

Non acceptance of technology may result in serious damages to organizations. For example, non acceptance of simulation technology cost Merrill Lynch Bank over {dollar}50 billion in 2008, while statistics in 2 separate studies showed that non acceptance of technology was responsible for a 57% decrease in performance level for physicians practicing in public tertiary hospitals in Hong Kong, and a 39% decrease in productivity for hotel workers in Seoul, Korea. The problem addressed in this research was non acceptance of simulation technology by project managers. This research investigated the correlation among personal innovativeness, organizational innovativeness, perceived usefulness, perceived ease of …

Using Organizational, Coordination, And Contingency Theories To Examine Project Manager Insights On Agile And Traditional Success Factors For Information Technology Projects, Michael J. Doherty

Walden Dissertations and Doctoral Studies

Two dominant research views addressing disappointing success rates for information technology (IT) projects suggest project success may depend on the presence of a large number of critical success factors or advocate for agile project management as an alternative to traditional practice. However, after two decades of research, success rates remain low, and the role of critical success factors or project management approach remains unclear. The purpose of this study was to use views of experienced project managers to explore the contribution of success factors and management approach to project success. Applying organizational, coordination, and contingency theories, the research questions examined …

Transcending Technological Innovation: The Impact Of Acquisitions On Entrepreneurial Technical Organizations, Bruce Crochetiere

Walden Dissertations and Doctoral Studies

Technology firms with substantial cash reserves acquire smaller entrepreneurial firms for diversification. In 2006, 3 large firms acquired 28 organizations, with the combined deals exceeding {dollar}4.7 billion. The problem addressed in this study is that new start-up companies with innovative ideas may not mature when they are acquired by larger companies and do not fully articulate potential industry-transcending innovation. This is important because the unsuccessful integration of an acquisition can dismantle innovation and compromises economic inventiveness. Drawing from the disruptive innovation and the resource-based theories, the purpose of the quasi-experimental study was to examine the impact of acquisition by larger …

An Examination Of Small Businesses' Propensity To Adopt Cloud-Computing Innovation, Steven E. Powelson

Walden Dissertations and Doctoral Studies

The problem researched was small business leaders' early and limited adoption of cloud computing. Business leaders that do not use cloud computing may forfeit the benefits of its lower capital costs and ubiquitous accessibility. Anchored in a diffusion of innovation theory, the purpose of this quantitative cross-sectional survey study was to examine if there is a relationship between small business leaders' view of cloud-computing attributes of compatibility, complexity, observability, relative advantage, results demonstrable, trialability, and voluntariness and intent to use cloud computing. The central research question involved understanding the extent to which each cloud-computing attribute relate to small business leaders' …

Investigating Student Gender And Grade Level Differences In Digital Citizenship Behavior, Robert Lyons

Walden Dissertations and Doctoral Studies

The rapid rise of technology, which has become embedded in all facets of 21st century society during the past decade, has fostered a corresponding rise in its misuse. Digital citizenship abuse, a relatively new phenomenon of this electronic age, is a rapidly growing global problem. Parents, schools, and society play roles in supporting appropriate online behavior. Schools must take the lead role to assess and address digital citizenship issues. This ex post facto study investigated the online actions of students in a medium-sized K-12 school district and explored possible causal relationships between online misbehavior and student grade and gender based …

Acceptance And Usage Of Electronic Health Record Systems In Small Medical Practices, Ritu Tannan

Walden Dissertations and Doctoral Studies

One of the objectives of the U.S. government has been the development of a nationwide health information infrastructure, including adoption and use of an electronic health records (EHR) system. However, a 2008 survey conducted by the National Center for Health Statistics indicated a 41.5% usage of the EHR system by physicians in office-based practices. The purpose of this study was to explore opinions and beliefs on the barriers to the diffusion of an ERH system using Q-methodology. Specifically, the research questions examined the subjectivity in the patterns of perspectives at the preadoption stage of the nonusers and at the postadoption …

The Potential Role Of Business Intelligence In Church Organizations, Charmaine Felder

Walden Dissertations and Doctoral Studies

Business intelligence (BI) involves transforming data into actionable information to make better business decisions that may help improve operations. Although businesses have experienced success with BI, how leaders of church organizations might be able to exploit the advantages of BI in church organizations remains largely unexplored. The purpose of the phenomenological study was to explore the perceptions of pastoral leaders concerning the potential usefulness of BI in church organizations. Conceptual support for the study was based on the premise that churches may also benefit from BI that helps improve decision making and organizational performance. Three research questions were used to …

Entropy In Postmerger And Acquisition Integration From An Information Technology Perspective, Gloria S. Williams

Walden Dissertations and Doctoral Studies

Mergers and acquisitions have historically experienced failure rates from 50% to more than 80%. Successful integration of information technology (IT) systems can be the difference between postmerger success or failure. The purpose of this phenomenological study was to explore the entropy phenomenon during postmerger IT integration. To that end, a purposive sample of 14 midlevel and first-line managers in a manufacturing environment was interviewed to understand how the negative effects of entropy affect the ultimate success of the IT integration process. Using the theoretical framework of the process school of thought, interview data were iteratively examined by using keywords, phrases, …

Data-Driven Decision Making As A Tool To Improve Software Development Productivity, Mary Erin Brown

Walden Dissertations and Doctoral Studies

The worldwide software project failure rate, based on a survey of information technology software manager's view of user satisfaction, product quality, and staff productivity, is estimated to be between 24% and 36% and software project success has not kept pace with the advances in hardware. The problem addressed by this study was the limited information about software managers' experiences with data-driven decision making (DDD) in agile software organizations as a tool to improve software development productivity. The purpose of this phenomenological study was to explore how agile software managers view DDD as a tool to improve software development productivity and …

Learning Without Onboarding: How Assessing And Evaluating Learning Benefits New Information Technology Hires, Dory L. Morris

Walden Dissertations and Doctoral Studies

Onboarding ensures learning success through sharing and acquiring knowledge to remain competitive. However, little is known about new Information Technology (IT) hires' learning needs in the absence of onboarding; therefore, the purpose of this case study was to examine, increase, and retain their technical knowledge at the Unified Communications Company (UCC). Following the theoretical model of knowledge management, which holds that knowledge is the key to confirm learning and knowledge sharing, the research questions were used to examine how the company assessed and increased their technical knowledge and how they taught their culture in the absence of onboarding. A qualitative …

Asset Reuse Of Images From A Repository, Deirdre Herman

Walden Dissertations and Doctoral Studies

According to Markus's theory of reuse, when digital repositories are deployed to collect and distribute organizational assets, they supposedly help ensure accountability, extend information exchange, and improve productivity. Such repositories require a large investment due to the continuing costs of hardware, software, user licenses, training, and technical support. The problem addressed in this study was the lack of evidence in the literature on whether users in fact reused enough digital assets in repositories to justify the investment. The objective of the study was to investigate the organizational value of repositories to better inform architectural, construction, software and other industries whether …

The Relationship Between Cell Phone Use And Identity Theft, Lewis O. Saunders

Walden Dissertations and Doctoral Studies

The growth of mobile phone use has paralleled increased reports of identity theft. Identity theft can result in financial loss and threats to a victim's personal safety. Although trends in identity theft are well-known, less is known about individual cell phone users' attitudes toward identity theft and the extent to which they connect it to cell phone use. The purpose of this qualitative study was to determine how cell phone use is affected by attitudes toward privacy and identity theft. The study was based on social impact theory, according to which people's attitudes and behavior are affected by the strength …

Exploring Identity Management At Community Colleges In Texas With Open Access To College Computer Networks, Michael John Callahan

Walden Dissertations and Doctoral Studies

The study addressed the lack of identity management practices in Texas community colleges to identify guest users who access college computers. Guest user access is required by Texas law and is part of the state's mission to bridge the technology gap; however, improper identification methods leave the college vulnerable to liability issues. The purpose of this study was to eliminate or mitigate liabilities facing colleges by creating and using security policies to identify guest users. This study combined the theoretical concepts of Cameron's internal security management model with the external trust models of the Liberty Alliance and Microsoft's Passport software. …

Randomly Projected Kd-Trees With Distance Metric Learning For Image Retrieval, Pengcheng Wu, Steven Hoi, Duc Dung Nguyen, Ying He

Research Collection School Of Computing and Information Systems

Efficient nearest neighbor (NN) search techniques for highdimensional data are crucial to content-based image retrieval (CBIR). Traditional data structures (e.g., kd-tree) usually are only efficient for low dimensional data, but often perform no better than a simple exhaustive linear search when the number of dimensions is large enough. Recently, approximate NN search techniques have been proposed for high-dimensional search, such as Locality-Sensitive Hashing (LSH), which adopts some random projection approach. Motivated by similar idea, in this paper, we propose a new high dimensional NN search method, called Randomly Projected kd-Trees (RP-kd-Trees), which is to project data points into a lower-dimensional …

When Machines Are Watching: How Warrantless Use Of Gps Surveillance Technology Violates The Fourth Amendment Right Against Unreasonable Searches, David Thaw, Priscilla Smith, Nabiha Syed, Albert Wong

Articles

Federal and state law enforcement officials throughout the nation are currently using Global Positioning System (GPS) technology for automated, prolonged surveillance without obtaining warrants. As a result, cases are proliferating in which criminal defendants are challenging law enforcement’s warrantless uses of GPS surveillance technology, and courts are looking for direction from the Supreme Court. Most recently, a split has emerged between the Ninth and D.C. Circuit Courts of Appeal on the issue. In United States v. Pineda-Moreno, the Ninth Circuit relied on United States v. Knotts — which approved the limited use of beeper technology without a warrant — to …

An Evaluation Of The Usability Of A Computerized Decision Support System For Nursing Homes, M. Fossum, M. Ehnfors, Ann L. Fruhling, A. Ehrenberg

Interdisciplinary Informatics Faculty Publications

Background: Computerized decision support systems (CDSSs) have the potential to significantly improve the quality of nursing care of older people by enhancing the decision making of nursing personnel. Despite this potential, health care organizations have been slow to incorporate CDSSs into nursing home practices.

Objective: This study describes facilitators and barriers that impact the ability of nursing personnel to effectively use a clinical CDSS for planning and treating pressure ulcers (PUs) and malnutrition and for following the suggested risk assessment guidelines for the care of nursing home residents.

Methods: We employed a qualitative descriptive design using varied …

Spatial Queries In The Presence Of Obstacles, Jun Zhang, Dimitris Papadias, Kyriakos Mouratidis, Manli Zhu

Kyriakos MOURATIDIS

Despite the existence of obstacles in many database applications, traditional spatial query processing utilizes the Euclidean distance metric assuming that points in space are directly reachable. In this paper, we study spatial queries in the presence of obstacles, where the obstructed distance between two points is defined as the length of the shortest path that connects them without crossing any obstacles. We propose efficient algorithms for the most important query types, namely, range search, nearest neighbors, e-distance joins and closest pairs, considering that both data objects and obstacles are indexed by R-trees. The effectiveness of the proposed solutions is verified …

Tree-Based Partition Querying: A Methodology For Computing Medoids In Large Spatial Datasets, Kyriakos Mouratidis, Dimitris Papadias, Spiros Papadimitriou

Kyriakos MOURATIDIS

Besides traditional domains (e.g., resource allocation, data mining applications), algorithms for medoid computation and related problems will play an important role in numerous emerging fields, such as location based services and sensor networks. Since the k-medoid problem is NP hard, all existing work deals with approximate solutions on relatively small datasets. This paper aims at efficient methods for very large spatial databases, motivated by: (i) the high and ever increasing availability of spatial data, and (ii) the need for novel query types and improved services. The proposed solutions exploit the intrinsic grouping properties of a data partition index in order …

Partially Materialized Digest Scheme: An Efficient Verification Method For Outsourced Databases, Kyriakos Mouratidis, Dimitris Sacharidis, Hwee Hwa Pang

Kyriakos MOURATIDIS

In the outsourced database model, a data owner publishes her database through a third-party server; i.e., the server hosts the data and answers user queries on behalf of the owner. Since the server may not be trusted, or may be compromised, users need a means to verify that answers received are both authentic and complete, i.e., that the returned data have not been tampered with, and that no qualifying results have been omitted. We propose a result verification approach for one-dimensional queries, called Partially Materialized Digest scheme (PMD), that applies to both static and dynamic databases. PMD uses separate indexes …

Preventing Location-Based Identity Inference In Anonymous Spatial Queries, Panos Kalnis, Gabriel Ghinita, Kyriakos Mouratidis, Dimitris Papadias

Kyriakos MOURATIDIS

The increasing trend of embedding positioning capabilities (for example, GPS) in mobile devices facilitates the widespread use of location-based services. For such applications to succeed, privacy and confidentiality are essential. Existing privacy-enhancing techniques rely on encryption to safeguard communication channels, and on pseudonyms to protect user identities. Nevertheless, the query contents may disclose the physical location of the user. In this paper, we present a framework for preventing location-based identity inference of users who issue spatial queries to location-based services. We propose transformations based on the well-established K-anonymity concept to compute exact answers for range and nearest neighbor search, without …

Anonymous Query Processing In Road Networks, Kyriakos Mouratidis, Man Lung Yiu

Kyriakos MOURATIDIS

The increasing availability of location-aware mobile devices has given rise to a flurry of location-based services (LBSs). Due to the nature of spatial queries, an LBS needs the user position in order to process her requests. On the other hand, revealing exact user locations to a (potentially untrusted) LBS may pinpoint their identities and breach their privacy. To address this issue, spatial anonymity techniques obfuscate user locations, forwarding to the LBS a sufficiently large region instead. Existing methods explicitly target processing in the euclidean space and do not apply when proximity to the users is defined according to network distance …

On-Line Discovery Of Hot Motion Paths, Dimitris Sacharidis, Kostas Patroumpas, Manolis Terrovitis, Verena Kantere, Michalis Potamias, Kyriakos Mouratidis, Timos Sellis

Kyriakos MOURATIDIS

We consider an environment of numerous moving objects, equipped with location-sensing devices and capable of communicating with a central coordinator. In this setting, we investigate the problem of maintaining hot motion paths, i.e., routes frequently followed by multiple objects over the recent past. Motion paths approximate portions of objects' movement within a tolerance margin that depends on the uncertainty inherent in positional measurements. Discovery of hot motion paths is important to applications requiring classification/profiling based on monitored movement patterns, such as targeted advertising, resource allocation, etc. To achieve this goal, we delegate part of the path extraction process to objects, …

Efficient Evaluation Of Multiple Preference Queries, Hou U Leong, Nikos Mamaoulis, Kyriakos Mouratidis

Kyriakos MOURATIDIS

Consider multiple users searching for a hotel room, based on size, cost, distance to the beach, etc. Users may have variable preferences expressed by different weights on the attributes of the searched objects. Although individual preference queries can be evaluated by selecting the object in the database with the highest aggregate score, in the case of multiple requests at the same time, a single object cannot be assigned to more than one users. The challenge is to compute a fair 1-1 matching between the queries and a subset of the objects. We model this as a stable-marriage problem and propose …

Scalable Verification For Outsourced Dynamic Databases, Hwee Hwa Pang, Jilian Zhang, Kyriakos Mouratidis

Kyriakos MOURATIDIS

Query answers from servers operated by third parties need to be verified, as the third parties may not be trusted or their servers may be compromised. Most of the existing authentication methods construct validity proofs based on the Merkle hash tree (MHT). The MHT, however, imposes severe concurrency constraints that slow down data updates. We introduce a protocol, built upon signature aggregation, for checking the authenticity, completeness and freshness of query answers. The protocol offers the important property of allowing new data to be disseminated immediately, while ensuring that outdated values beyond a pre-set age can be detected. We also …

Continuous Nearest Neighbor Queries Over Sliding Windows, Kyriakos Mouratidis, Dimitris Papadias

Kyriakos MOURATIDIS

Recent research has focused on continuous monitoring of nearest neighbors (NN) in highly dynamic scenarios, where the queries and the data objects move frequently and arbitrarily. All existing methods, however, assume the Euclidean distance metric. In this paper we study k-NN monitoring in road networks, where the distance between a query and a data object is determined by the length of the shortest path connecting them. We propose two methods that can handle arbitrary object and query moving patterns, as well as fluctuations of edge weights. The first one maintains the query results by processing only updates that may invalidate …

K-Anonymity In The Presence Of External Databases, Dimitris Sacharidis, Kyriakos Mouratidis, Dimitris Papadias

Kyriakos MOURATIDIS

The concept of k-anonymity has received considerable attention due to the need of several organizations to release microdata without revealing the identity of individuals. Although all previous k-anonymity techniques assume the existence of a public database (PD) that can be used to breach privacy, none utilizes PD during the anonymization process. Specifically, existing generalization algorithms create anonymous tables using only the microdata table (MT) to be published, independently of the external knowledge available. This omission leads to high information loss. Motivated by this observation we first introduce the concept of k-join-anonymity (KJA), which permits more effective generalization to reduce the …

Aggregate Nearest Neighbor Queries In Spatial Databases, Dimitris Papadias, Yufei Tao, Kyriakos Mouratidis, Chun Kit Hui

Kyriakos MOURATIDIS

Given two spatial datasets P (e.g., facilities) and Q (queries), an aggregate nearest neighbor (ANN) query retrieves the point(s) of P with the smallest aggregate distance(s) to points in Q. Assuming, for example, n users at locations q1,...qn, an ANN query outputs the facility p belongs to P that minimizes the sum of distances |pqi| for 1 is less than or equal to i is less than or equal to n that the users have to travel in order to meet there. Similarly, another ANN query may report the point p belongs to P that minimizes the maximum distance that …

Continuous Medoid Queries Over Moving Objects, Stavros Papadopoulos, Dimitris Sacharidis, Kyriakos Mouratidis

Kyriakos MOURATIDIS

In the k-medoid problem, given a dataset P, we are asked to choose kpoints in P as the medoids. The optimal medoid set minimizes the average Euclidean distance between the points in P and their closest medoid. Finding the optimal k medoids is NP hard, and existing algorithms aim at approximate answers, i.e., they compute medoids that achieve a small, yet not minimal, average distance. Similarly in this paper, we also aim at approximate solutions. We consider, however, the continuous version of the problem, where the points in P move and our task is to maintain the medoid set on-the-fly …

Query Processing In Spatial Databases Containing Obstacles, Jun Zhang, Dimitris Papadias, Kyriakos Mouratidis, Manli Zhu

Kyriakos MOURATIDIS

Despite the existence of obstacles in many database applications, traditional spatial query processing assumes that points in space are directly reachable and utilizes the Euclidean distance metric. In this paper, we study spatial queries in the presence of obstacles, where the obstructed distance between two points is defined as the length of the shortest path that connects them without crossing any obstacles. We propose efficient algorithms for the most important query types, namely, range search, nearest neighbours, e-distance joins, closest pairs and distance semi-joins, assuming that both data objects and obstacles are indexed by R-trees. The effectiveness of the proposed …