Kinh Nguyen

POLG mutations in Alpers syndrome.

Described are six patients with Alpers syndrome from four unrelated families. Affected individuals harbored the following combinations of POLG mutations: 1) A467T/W1020X, 2) W748S-E1143G/G848S, 3) A467T/A467T, and 4) A467T/G848S. Homozygosity for the A467T allele in one patient was associated with a later age at onset. Mitochondrial respiratory chain studies in skeletal muscle were normal in each case. Nine combinations of mutant POLG alleles that cause Alpers syndrome are summarized.

Double-layered schema integration of heterogeneous XML sources

Schema integration aims to create a mediated schema as a unified representation of existing heterogeneous sources sharing a common application domain. These sources have been increasingly written in XML due to its versatility and expressive power. Unfortunately, these sources often use different elements and structures to express the same concepts and relations, thus causing substantial semantic and structural conflicts. Such a challenge impedes the creation of high-quality mediated schemas and has not been adequately addressed by existing integration methods. In this paper, we propose a novel method, named XINTOR, for automating the integration of heterogeneous schemas. Given a set of XML sources and a set of correspondences between the source schemas, our method aims to create a complete and minimal mediated schema: it completely captures all of the concepts and relations in the sources without duplication, provided that the concepts do not overlap. Our contributions are fourfold. First, we resolve structural conflicts inherent in the source schemas. Second, we introduce a new statistics-based measure, called path cohesion, for selecting concepts and relations to be a part of the mediated schema. The path cohesion is statistically computed based on multiple path quality dimensions such as average path length and path frequency. Third, we resolve semantic conflicts by augmenting the semantics of similar concepts with context-dependent information. Finally, we propose a novel double-layered mediated schema to retain a wider range of concepts and relations than existing mediated schemas, which are at best either complete or minimal, but not both. Performed on both real and synthetic datasets, our experimental results show that XINTOR outperforms existing methods with respect to (i) the mediated-schema quality using precision, recall, F-measure, and schema minimality; and (ii) the execution performance based on execution time and scale-up performance.

Peer-to-peer bichromatic reverse nearest neighbours in mobile ad-hoc networks

The increasing use of mobile communications has raised many issues of decision support and resource allocation. A crucial problem is how to solve queries of Reverse Nearest Neighbour (RNN). An RNN query returns all objects that consider the query object as their nearest neighbour. Existing methods mostly rely on a centralised base station. However, mobile P2P systems offer many benefits, including self-organisation, fault-tolerance and load-balancing. In this study, we propose and evaluate 3 distinct P2P algorithms focusing on bichromatic RNN queries, in which mobile query peers and static objects of interest are of two different categories, based on a time-out mechanism and a boundary polygon around the mobile query peers. The Brute-Force Search Algorithm provides a naive approach to exploit shared information among peers whereas two other Boundary Search Algorithms filter a number of peers involved in query processing. The algorithms are evaluated in the MiXiM simulation framework with both real and synthetic datasets. The results show the practical feasibility of the P2P approach for solving bichromatic RNN queries for mobile networks. Introducing a new direction in mobile P2P query processing for RNN queries.Proposing and evaluating three different search algorithms: BFA, RBA and TBA.Substantially saving more time and energy compared with the centralised system.TBA outperforms by filtering unnecessary peers and maintaining high accuracy rate.

XMiner: Mining XML Mediated Schemas

This paper presents a novel schema mediation approach, called XMiner, for mining mediated schemas from a set of XML schemas. XMiner addresses three main problems resulting from the heterogeneous source schemas: nesting discrepancy, backward paths and schema discrepancy. XMiner discovers frequent substructures using frequent subtree mining algorithms, and then constructs a mediated schemas. XMiner aims to preserve the hierarchical structure as the best as possible while avoiding information loss. XMiner exploits structural context, forward/backward paths, and label semantics for matching, mapping and merging frequent substructures. Experiments on real and synthetic datasets are reported to show that XMiner offers acceptable performance and quality for large-scale application scenarios.

Mediation-Based XML Query Answerability

This paper presents a novel mediation-based query answering approach which allows users (1) to reuse their own predefined queries to retrieve information properly from their local data source, and (2) to reformulate those queries in terms of remote data sources in order to obtain additional relevant information. The problem of structural diversity in XML design (e.g. nesting discrepancy and backward paths) makes it difficult to reformulate the queries. Therefore, we highlight the importance of precise query rewriting using composite concepts and relations of the mediated schema. Our experimental evaluations on real application datasets show that our approach effectively obtains correct answers over a broad diversity of schemas.

The concept of web event and a practical model‐driven approach to web information system development

This article proposes the concept of web clientserver event together with its associated taxonomy which yields a formal specification for such an event. The concept, in conjunction with the concept of atomic use case (reviewed in the article), is then used as a key element for a model‐driven approach to web information system development. The outcome is a new method for web information systems development that reduces the complex web‐based hypermedia navigation behaviour to a much simpler event‐driven behaviour. On the strength of that realized simplicity, the method provides (i) a set of platform‐independent models that completely characterizes the application, and (ii) a well‐defined process to map the combined model to any chosen platform‐dependent implementation.

Atomic Use Case: A Concept for Precise Modelling of Object-Oriented Information Systems

We propose the concept of “atomic use case” and demonstrate how this concept can be used to bring the analysis of functional requirements of information systems to a much deeper level than usual, and ultimately to construct a precise specification of the system’s functionality. Specifically, the complete functionality of an information system is defined by a set of atomic use cases, which are consistently specified in terms of their input, output, pre- and postcondition.

Vertical Indexing for Moving Objects in Multifloor Environments

The indexing and tracking of objects moving in indoor spaces has increasingly become an important area of research, which presents a fundamentally different challenge. There are two main reasons for why indoor should be treated as cellular space. Firstly, an indoor space has entities, such as rooms and walls, that constrain the movement of the moving objects. Secondly, the relevant notion of locations of an object is cell based rather than an exact Euclidean coordinate. As a solution, in our earlier works, we proposed a cell-based indexing structure, called the C-tree, for indexing objects moving in indoor space. In this paper, we extend the C-tree to solve another interesting problem. It can be observed that many indoor spaces (such as shopping centers) contain wings/sections. For such a space, there are queries for which the wing/section location of an object, rather than the cellular location, is the relevant answer (e.g., “the object is in the east wing”). In this paper, we propose a new index structure, called the GMI-tree (“GMI” stands for “Graph-based Multidimensional Index”). The GMI-tree is based on two notions of distance, or equivalently, two notions of adjacency: one represents horizontal adjacency and the other represents vertical adjacency.

Cross product line reuse in Component-Based Software Engineering

Over the last twenty years, our understanding of how software systems can be developed as product lines has improved significantly. However, there has been little progress towards a wider goal of product lines that are usable across disparate application domains. We present a new formalism, a Nature Diagram, to address this issue. This representation allows the characteristics (both data structures and operations) of entities identified during the design process to be represented and easily compared in a way that allows their usability in domains other than their original “home” to be identified. The approach is inspired by the natural ability of human designers to discover similarities between systems. We validate our method using two real world examples, and illustrate its advantages by comparison with existing methods.

Automated generation of structural design models from SBVR specification

Business rules play a critical role in developing effective and flexible information systems. In light of this critical role, the publication of the Semantic Business Vocabulary and Business Rules standard (SBVR) is considered a highly significant advance. However, although SBVR is a major breakthrough in defining business vocabulary and rules, its subsequent adoption in practical applications has proved to be much slower than originally anticipated. This paper proposes an approach that firstly reduces the SBVR complexity by identifying a subset that can be used to express structural design models unambiguously. Secondly, it formalizes a transformation that maps the identified SBVR subset to the UML class diagram, based on formally defined and validated meta-models that can guarantee the correctness of the generated UML class model. Finally, it incorporates the formal meta-models and the formal transformation algorithm into an automated transformation tool. The proposed approach is evaluated by taking into consideration the aspects of applicability, functionality, correctness, and completeness through a number of case studies and a comparison with an existing transformation approach.