Flexible querying of semistructured data: A fuzzy-set-based approach

This article provides a general discussion about how flexible querying can be applied to semistructured data (SSD). We adapt flexible querying ideas, already used for classically structured databases, to XQuery-like querying of SSD for managing users' priority and preferences, but also for tackling with the variability of SSD underlying structures. Indeed flexible querying seems to be still more useful for SSD than for classical databases, because of the potential structural heterogeneity of the former. Fuzzy sets are useful for expressing flexible requirements on attribute values and for estimating the degree of similarity of tags, or attribute labels, with elements present in the request. Priorities are introduced in the request for specifying the relative importance of elementary requirements in terms of their semantic contents, but also preferences about the location of information in the structure. The evaluation of the queries uses a qualitative scale with a finite number of levels, and retrieved pieces of SSD are rank-ordered using a lexicographic vector procedure. Illustrative examples are provided. © 2007 Wiley Periodicals, Inc. Int J Int Syst 22: 723–737, 2007.     

Design and implementation of index structures for fuzzy spatial databases

Over the years database management systems have evolved to include spatially referenced data. Because spatial data are complex and have a number of unique constraints (i.e., spatial components and uncertain properties), spatial database systems can be effective only if the spatial data are properly handled at the physical level. Therefore, it is important to develop an effective spatial and aspatial indexing technique to facilitate flexible spatial and/or aspatial querying for such databases. For this purpose we introduce an indexing approach to use (fuzzy) spatial and (fuzzy) aspatial data. We use a number of spatial index structures, such as Multilevel Grid File (MLGF), G-tree, R-tree, and R^*-tree, for fuzzy spatial databases and compare the performances of these structures for various flexible queries. © 2007 Wiley Periodicals, Inc. Int J Int Syst 22: 805–826, 2007.     

Introducing fuzziness in object models and database interfaces through aspects

Imperfection in information can be considered a crosscutting concern that manifests itself in diverse kinds of imprecision, uncertainty, or inconsistency in the data models of a software system. The extension of existing programming and querying interfaces for the different aspects of information imperfection requires a proper modularization of the different concerns of numerical imprecision handling, so that the extensions do not interfere with existing programming practices and do not obscure the original design. Aspect‐oriented design (AOD) enables such a form of nonintrusive extensions to be added to existing software libraries, clearly separating fuzziness or other imperfections in data as a differentiated concern that can be considered from the early phases of development. In this article, a general framework for aspect‐based extension of data models and fuzzy databases is described, and some design and implementation issues of such AOD‐based extensions on OJB database libraries are described as a case study. © 2006 Wiley Periodicals, Inc. Int J Int Syst 21: 1199–1216, 2006.     

Clustering web search results using fuzzy ants

Algorithms for clustering Web search results have to be efficient and robust. Furthermore they must be able to cluster a data set without using any kind of a priori information, such as the required number of clusters. Clustering algorithms inspired by the behavior of real ants generally meet these requirements. In this article we propose a novel approach to ant‐based clustering, based on fuzzy logic. We show that it improves existing approaches and illustrates how our algorithm can be applied to the problem of Web search results clustering. © 2007 Wiley Periodicals, Inc. Int J Int Syst 22: 455–474, 2007.     

Updating extended possibility‐based fuzzy relational databases

Two kinds of fuzziness in attribute values of the fuzzy relational databases can be distinguished: one is that attribute values are possibility distributions and the other is that there are resemblance relations in attribute domains. The fuzzy relational databases containing these two kinds of fuzziness simultaneously are called extended possibility‐based fuzzy relational databases. In this article, we focus on such fuzzy relational databases and investigate three update operations for the fuzzy relational databases, which are Insertion, Deletion, and Modification, respectively. We develop the strategies and implementation algorithms of these operations. © 2007 Wiley Periodicals, Inc. Int J Int Syst 22: 237–258, 2007.     

Attribute-oriented fuzzy generalization in proximity- and similarity-based relational database systems

In this article we investigate an attribute-oriented induction approach for acquisition of abstract knowledge from data stored in a fuzzy database environment. We utilize a proximity-based fuzzy database schema as the medium carrying the original information, where lack of precise information about an entity can be reflected via multiple attribute values, and the classical equivalence relation is replaced with the broader fuzzy proximity relation. We analyze in detail the process of attribute-oriented induction by concept hierarchies, utilizing the original properties of fuzzy databases to support this established data mining technique. In our approach we take full advantage of the implicit knowledge about the similarity of original attribute values, included by default in the investigated fuzzy database schemas. © 2007 Wiley Periodicals, Inc. Int J Int Syst 22: 763–779, 2007.     

Estimating the performance of multidimensional access methods based on nonoverlapping regions

Most cost models for the prediction of the performance of multidimensional access methods are based on Minkowski operations. However, this approach does not correspond to the space‐partitioning strategy of multidimensional access methods that produce nonoverlapping index regions, for example, the KDB‐tree and its variants. This article proposes a new cost model for the prediction of the selection (search) performance of the related access methods, including its adaptation for nonuniform data. The results of an extensive set of experiments conducted on both simulated and real data show that the cost model and its extension provide a basis for a highly accurate analysis of these structures in both low‐ and high‐dimensional situations. © 2007 Wiley Periodicals, Inc. Int J Int Syst 22: 259–277, 2007.     

Intelligent e‐government services with personalized recommendation techniques

Information overload is becoming one of the problems that hinder the effectiveness of e‐government services. Intelligent e‐government services with personalized recommendation techniques can provide a solution for this problem. Existing recommendation approaches have not entirely considered the influences of attributes of various online services and may result in no guarantee of recommendation accuracy. This study proposes a new approach to handle recommendation issues of one‐and‐only items in e‐government services. The proposed approach integrates the techniques of semantic similarity and the traditional item‐based collaborative filtering. A recommender system named Smart Trade Exhibition Finder has been developed to implement the proposed recommendation approach. The recommender system can be applied in e‐government services to improve the quality of government‐to‐business online services. © 2007 Wiley Periodicals, Inc. Int J Int Syst 22: 401–417, 2007.     

An evolutionary strategy for decremental multiobjective optimization problems

In this article, an evolutionary algorithm for multiobjective optimization problems in a dynamic environment is studied. In particular, we focus on decremental multiobjective optimization problems, where some objectives may be deleted during evolution—for such a process we call it objective decrement. It is shown that the Pareto‐optimal set after objective decrement is actually a subset of the Pareto‐optimal set before objective decrement. Based on this observation, the inheritance strategy is suggested. When objective decrement takes place, this strategy selects good chromosomes according to the decremented objective set from the solutions found before objective decrement, and then continues to optimize them via evolution for the decremented objective set. The experimental results showed that this strategy can help MOGAs achieve better performance than MOGAs without using the strategy, where the evolution is restarted when objective decrement occurs. More solutions with better quality are found during the same time span. © 2007 Wiley Periodicals, Inc. Int J Int Syst 22: 847–866, 2007.     

Increasing fuzzy rules cooperation based on evolutionary adaptive inference systems

This article presents a study on the use of parametrized operators in the Inference System of linguistic fuzzy systems adapted by evolutionary algorithms, for achieving better cooperation among fuzzy rules. This approach produces a kind of rule cooperation by means of the inference system, increasing the accuracy of the fuzzy system without losing its interpretability. We study the different alternatives for introducing parameters in the Inference System and analyze their interpretation and how they affect the rest of the components of the fuzzy system. We take into account three applications in order to analyze their accuracy in practice. © 2007 Wiley Periodicals, Inc. Int J Int Syst 22: 1035–1064, 2007.     

Design of optimum gain pyramidal horn with improved formulas using particle swarm optimization

In this article, a new method to design an optimum gain horn antenna is presented. This method is based on improving existing design equations along with the use of particle swarm optimization technique. The obtained results are more accurate than those available in the literature since no path length error approximation is involved. Improved horn dimensions, for different 15 designs, are obtained which give the desired gain almost exactly. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

Fuzzy multi‐attribute cost–benefit analysis of e‐services

E‐service evaluation is a complex problem in which many qualitative attributes must be considered. These kinds of attributes make the evaluation process hard and vague. Cost–benefit analyses applied to various areas are usually based on the data under certainty or risk. In case of uncertain, vague, and/or linguistic data, the fuzzy set theory can be used to handle the analysis. In this article, after the evaluation attributes of e‐services and the fuzzy multi‐attribute decision‐making methods are introduced, a fuzzy hierarchical TOPSIS model is developed and applied to an e‐service provider selection problem with some sensitivity analyses. The developed model is a useful tool for the companies that prefer outsourcing for e‐activities. It is shown that service systems can be effectively evaluated by the proposed method. © 2007 Wiley Periodicals, Inc. Int J Int Syst 22: 547–565, 2007.     

Knowledge provision with intelligent e‐services

Interorganizational knowledge networks and knowledge marketplaces have emerged to enable organizations to share or commercially exploit their knowledge outside narrow organizational borders. The materialization of these structures requires concrete and sound mechanisms for the efficient external provision of knowledge stored in knowledge repositories within the organization. In our approach, we employ semantic Web services as a vehicle for publishing knowledge repositories. We propose “knowledge provision services” as a means for efficient retrieval and composition of knowledge objects from knowledge repositories of various organizational contexts regardless of the environment within which they are delivered. In this direction, we have extended OWL‐S with a knowledge object ontology, which represents knowledge objects in a generic, application‐neutral way, and we have developed an infrastructure for the publication, discovery, composition, and delivery of Knowledge Provision Services founded on the Web services architecture. © 2007 Wiley Periodicals, Inc. Int J Int Syst 22: 501–518, 2007.     

A fuzzy logic approach to experience‐based reasoning

Experience‐based reasoning (EBR) is a reasoning paradigm that has been used in almost every human activity such as business, military missions, and teaching activities since early human history. However, EBR has not been seriously studied from either a logical or mathematical viewpoint, although case‐based reasoning (CBR) researchers have paid attention to EBR to some extent. This article will attempt to fill this gap by providing a unified fuzzy logic‐based treatment of EBR. More specifically, this article first reviews the logical approach to EBR, in which eight different rules of inference for EBR are discussed. Then the article proposes fuzzy logic‐based models to these eight different rules of inference that constitute the fundamentals for all EBR paradigms from a fuzzy logic viewpoint, and therefore will form a theoretical foundation for EBR. The proposed approach will facilitate research and development of EBR, fuzzy systems, intelligent systems, knowledge management, and experience management. © 2007 Wiley Periodicals, Inc. Int J Int Syst 22: 867–889, 2007.     

Effective linearization technique for amplifiers operating close to saturation

The linearization technique that uses simultaneous injection of the second harmonics into the amplifier input and their feedforwarding to the amplifier output is suggested. This technique reduces the third‐order intermodulation products in multichannel amplifiers when amplifiers operate closer to saturation. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

nk‐bags

We generalize the concept of bags by introducing the notion of n^k‐bags with membership functions ranging in P(N), the power set of positive integers. Consequently, a number of operations on n^k‐bags are defined and some characterizations are done. © 2007 Wiley Periodicals, Inc. Int J Int Syst 22: 223–236, 2007.     

Active network architecture and management

Access and retrieval of meteorological and oceanographic data from heterogeneous sources in a distributed system presents many issues. There are a number of features of the TEDServices system that illustrate active network management for such data. There is a self-aware or intelligent aspect with respect to the mechanisms for shutdown, data ordering, and propagation of data orders. Intelligent cache management and collaborative application sharing process are other features of the active network management. Additionally a very important capability is the implementation of resumable object streams, which allows either the client or server side of a request to lose network connection, regain it, and the request will continue where it left off. © 2007 Wiley Periodicals, Inc. Int J Int Syst 22: 1123–1138, 2007.     

An argument‐dependent approach to determining OWA operator weights based on the rule of maximum entropy

The methods for determining OWA operator weights have aroused wide attention. We first review the main existing methods for determining OWA operator weights. We next introduce the principle of maximum entropy for setting up probability distributions on the basis of partial knowledge and prove that Xu's normal distribution‐based method obeys the principle of maximum entropy. Finally, we propose an argument‐dependent approach based on normal distribution, which assigns very low weights to these “false” or “biased” opinions and can relieve the influence of the unfair arguments. A numerical example is provided to illustrate the application of the proposed approach. © 2007 Wiley Periodicals, Inc. Int J Int Syst 22: 209–221, 2007.