Over the last decades computer based tools have been introduced to facilitate systems engineering processes. There are computer based tools for assisting engineers in virtually every aspect of the systems engineering process from requirement elicitation and analysis, over functional analysis, synthesis, implementation and verification. It is not uncommon for a tool to provide many services covering more than one aspect of systems engineering. There exist numerous situations where information exchanges across tool boundaries are valuable, e.g., exchange of specifications between organisations using heterogeneous tool sets, exchange of specifications from legacy to modern tools, exchange of pecifications to tools that provide more advanced modelling or analysis capabilities than the originating tool or storage of specification data in a neutral format such that multiple tools can operate on the data. The focus in this thesis is on the analysis, design and implementation of a method and tool neutral information model for enabling systems engineering tool data exchange. The information model includes support for representation of requirements, system functional architecture and physical architecture, and verification and validation data. There is also support for definition of multiple system viewpoints, representation of system architecture, traceability information and version and configuration management. The applicability of the information model for data exchange hasbeen validated through implementation of tool interfaces to COTS and proprietary systems engineering tools, and exchange of real specifications in different scenarios. The results obtained from the validation activities indicate that systems engineering tool data exchange may decrease the time spent for exchanging specifications between partners developing complex systems and that the information model approach described in the thesis is a compelling alternative to tool specific interfaces.

Despite recommender systems being useful, for some applications it is hard to accumulate all the required information needed for the recommendation. In today‟s ubiquitous environment, mobile devices with different characteristics are widely available. Our work focuses on the recommendation service built on mobile environment to support tourists‟ traveling need. When tourists visit a new attraction, their recommender systems can exchange data with the attraction system to help obtain rating information of people with similar tastes. Such asynchronous rating exchange mechanisms allow a tourist to receive ratings from other people even though they may not collocate at the same time. We proposed four data exchange methods between a user and an attraction system. Our recommendation mechanism incorporates other users‟ opinions to provide recommendations once the user has collected enough ratings. Every method is compared under four conditions which attraction systems carry different amount of existing data. Then we compare these methods under different amount of existing rating data and shed the light on their advantages and disadvantages. Finally, we compare our proposed asynchronous methods with other synchronous data exchange methods proposed previously.

Power industry is undergoing a transition from the traditional regulated environment to the competitive power market. To have a reliable state estimator (SE) in the power market environment, two major challenges are emerging, i.e. to keep SE running reliably even under a contingency and to run SE over a grid with extremely large size. The objective of this dissertation is to use graph theory to address the above two challenges. To keep SE running reliably under a contingency, a novel topological approach is first proposed to identify critical measurements and examine network observability under a contingency. To advance the classical topological observability analysis, a new concept of contingency observability graph (COG) is introduced and it is proven that a power system network maintains its observability under a contingency if and only if its COG satisfies some conditions. As an application of COG, a two-stage heuristic topological approach is further developed based on the new concept of qualified COG (QCOG) to minimize the number of measurements and RTUs under the constraint that the system remains observable under any single contingency. To overcome the disadvantages of existing SE over extremely large networks, a textured distributed state estimator (DSE), which consists of the off-line textured architecture design and the on-line textured computation, is proposed based on COG and a new concept of Bus Credibility Index (BCI). The textured DSE is non-recursive, asynchronous and avoids central controlling node. Numerical tests verify that the performance of the new textured DSE algorithm improves greatly compared with existing DSE algorithms in respect of bad data detection and identification. Furthermore, the software implementation for DSE is formulated as an information integration problem over regional power markets, and is very challenging because of its size and complexity. A new concept of semantic knowledge warehouse (SKW), together with the proposed concepts of semantic reasoning software component (SRSC) and deduction credibility, is developed to implement such an information integration system.

¡@¡@Recommendation techniques are developed to uncover users¡¥ real needs among large volume of information. Recommender systems help us filter information and present those similar to our tastes. As wireless technology develops and mobile devices become more and more powerful, new recommender systems appear to adapt to new implementation environment. We focus on travel recommender systems implemented in a mobile P2P environment using collaborative filtering recommendation algorithms which intend to provide real-time suggestions to travelers when they are on the move. Using the concept of incorporating other travelers¡¥ suggestions to the next attraction, we let users exchange their ratings toward visited attractions and use these ratings as a basis of recommendation. ¡@¡@We proposed six data exchange algorithms for travelers to exchange their ratings. The proposed methods were experimented in the homogeneous and heterogeneous environment. The experimental results show that the proposed data exchange methods have better recommendation hit ratio than content-based recommendation methods and better performance compared with other methods only using ratings of users when they meet face-to-face. Finally, all methods are compared and evaluated. An optimal method should be able to strike a balance between algorithm performance and the amount of data communication.

Various forms of information integration have become ubiquitous in current Business Intelligence (BI) technologies. In many cases, the semantic relationship between heterogeneous data sources is specified using high-level declarative rules, called schema mappings. For decades, Skolem functions have been regarded as an important tool in schema mappings as they permit a precise representation of incomplete information. The powerful mapping language of second-order tuple generating dependencies (SO tgds) permits arbitrary Skolem functions and has been proven to be the right class for modeling many integration problems, such as composition and correlation of mappings. This language is strictly more powerful than the languages used in many integration systems, including source-to-target and nested tgds which are both first-order (FO) languages (commonly known as GLAV and nested GLAV mappings). An important class of GLAV mappings are Local-As-View (LAV) tgds, which has found important application in data integration. These FO mapping languages are known to have more desirable programmatic and computational properties. In this thesis, we present a number of techniques for translating some SO tgds into equivalent, more manageable FO schema mappings. Our results rely on understanding and controlling the presence of incompleteness in mappings. We show that the composition of LAV mappings is not only FO, but can always be expressed as a LAV mapping. As a byproduct, we show that the problem of recovery checking for LAV mappings becomes tractable, in contrast to the case of GLAV mappings for which it is known to be undecidable. We introduce two approaches for transforming SO tgds into equivalent nested GLAV mappings. Our approach considers the presence of source constraints, and provides sufficient conditions for when the rich Skolem functions in SO tgds are well-behaved and have an FO semantics. We experimentally show that these conditions are able to handle a very large number of real schema mappings. Last, we propose a first-step for embracing incompleteness in the context of BI applications. Specifically, we present elements of a formal framework for vivifying data with respect to a business model. We view the task of discovering data-to-business interpretations as one of removing incompleteness from these mappings.

Various forms of information integration have become ubiquitous in current Business Intelligence (BI) technologies. In many cases, the semantic relationship between heterogeneous data sources is specified using high-level declarative rules, called schema mappings. For decades, Skolem functions have been regarded as an important tool in schema mappings as they permit a precise representation of incomplete information. The powerful mapping language of second-order tuple generating dependencies (SO tgds) permits arbitrary Skolem functions and has been proven to be the right class for modeling many integration problems, such as composition and correlation of mappings. This language is strictly more powerful than the languages used in many integration systems, including source-to-target and nested tgds which are both first-order (FO) languages (commonly known as GLAV and nested GLAV mappings). An important class of GLAV mappings are Local-As-View (LAV) tgds, which has found important application in data integration. These FO mapping languages are known to have more desirable programmatic and computational properties. In this thesis, we present a number of techniques for translating some SO tgds into equivalent, more manageable FO schema mappings. Our results rely on understanding and controlling the presence of incompleteness in mappings. We show that the composition of LAV mappings is not only FO, but can always be expressed as a LAV mapping. As a byproduct, we show that the problem of recovery checking for LAV mappings becomes tractable, in contrast to the case of GLAV mappings for which it is known to be undecidable. We introduce two approaches for transforming SO tgds into equivalent nested GLAV mappings. Our approach considers the presence of source constraints, and provides sufficient conditions for when the rich Skolem functions in SO tgds are well-behaved and have an FO semantics. We experimentally show that these conditions are able to handle a very large number of real schema mappings. Last, we propose a first-step for embracing incompleteness in the context of BI applications. Specifically, we present elements of a formal framework for vivifying data with respect to a business model. We view the task of discovering data-to-business interpretations as one of removing incompleteness from these mappings.

Thesis (M.S.)--California State University, Dominguez Hills, 1998. / Typescript (photocopy). "Spring 1998." Includes bibliographical references (leaf 39) and abstract.

O casamento entre esquemas XML e esquemas relacionais é necessário em diversas aplicações, tais como integração de informação e intercâmbio de dados. Tipicamente o casamento de esquemas é um processo manual, talvez suportado por uma interface grá ca. No entanto, o casamento manual de esquemas muito grandes é um processo dispendioso e sujeito a erros. Disto surge a necessidade de técnicas (semi)-automáticas de casamento de esquemas que auxiliem o usuário fornecendo sugestões de casamento, dessa forma reduzindo o esforço manual aplicado nesta tarefa. Apesar deste tema já ter sido estudado na literatura, o casamento entre esquemas XML e esquemas relacionais é ainda um tema em aberto. Isto porque os trabalhos existentes ou se aplicam para esquemas de nidos no mesmo modelo, ou são genéricos demais para o problema em questão. O objetivo desta dissertação é o desenvolvimento de técnicas especí cas para o casamento de esquemas XML e esquemas relacionais. Tais técnicas exploram as particularidades existentes entre estes esquemas para inferir valores de similaridade entre eles. As técnicas propostas são avaliadas através de experimentos com esquemas do mundo real. / The matching between XML schemas and relational schemas has many applications, such as information integration and data exchange. Typically, schema matching is done manually by domain experts, sometimes using a graphical tool. However, the matching of large schemas is a time consuming and error-prone task. The use of (semi-)automatic schema matching techniques can help the user in nding the correct matches, thereby reducing his labor. The schema matching problem has already been addressed in the literature. Nevertheless, the matching of XML schemas and relational schemas is still an open issue. This comes from the fact that the existing work is whether speci c for schemas designed in the same model, or too generic for the problem in discussion. The mais goal of this dissertation is to develop speci c techniques for the matching of XML schemas and relational schemas. Such techniques exploit the particularities found when analyzing the two schemas together, and use these cues to leverage the matching process. The techniques are evaluated by running experiments with real-world schemas.

O casamento entre esquemas XML e esquemas relacionais é necessário em diversas aplicações, tais como integração de informação e intercâmbio de dados. Tipicamente o casamento de esquemas é um processo manual, talvez suportado por uma interface grá ca. No entanto, o casamento manual de esquemas muito grandes é um processo dispendioso e sujeito a erros. Disto surge a necessidade de técnicas (semi)-automáticas de casamento de esquemas que auxiliem o usuário fornecendo sugestões de casamento, dessa forma reduzindo o esforço manual aplicado nesta tarefa. Apesar deste tema já ter sido estudado na literatura, o casamento entre esquemas XML e esquemas relacionais é ainda um tema em aberto. Isto porque os trabalhos existentes ou se aplicam para esquemas de nidos no mesmo modelo, ou são genéricos demais para o problema em questão. O objetivo desta dissertação é o desenvolvimento de técnicas especí cas para o casamento de esquemas XML e esquemas relacionais. Tais técnicas exploram as particularidades existentes entre estes esquemas para inferir valores de similaridade entre eles. As técnicas propostas são avaliadas através de experimentos com esquemas do mundo real. / The matching between XML schemas and relational schemas has many applications, such as information integration and data exchange. Typically, schema matching is done manually by domain experts, sometimes using a graphical tool. However, the matching of large schemas is a time consuming and error-prone task. The use of (semi-)automatic schema matching techniques can help the user in nding the correct matches, thereby reducing his labor. The schema matching problem has already been addressed in the literature. Nevertheless, the matching of XML schemas and relational schemas is still an open issue. This comes from the fact that the existing work is whether speci c for schemas designed in the same model, or too generic for the problem in discussion. The mais goal of this dissertation is to develop speci c techniques for the matching of XML schemas and relational schemas. Such techniques exploit the particularities found when analyzing the two schemas together, and use these cues to leverage the matching process. The techniques are evaluated by running experiments with real-world schemas.

O casamento entre esquemas XML e esquemas relacionais é necessário em diversas aplicações, tais como integração de informação e intercâmbio de dados. Tipicamente o casamento de esquemas é um processo manual, talvez suportado por uma interface grá ca. No entanto, o casamento manual de esquemas muito grandes é um processo dispendioso e sujeito a erros. Disto surge a necessidade de técnicas (semi)-automáticas de casamento de esquemas que auxiliem o usuário fornecendo sugestões de casamento, dessa forma reduzindo o esforço manual aplicado nesta tarefa. Apesar deste tema já ter sido estudado na literatura, o casamento entre esquemas XML e esquemas relacionais é ainda um tema em aberto. Isto porque os trabalhos existentes ou se aplicam para esquemas de nidos no mesmo modelo, ou são genéricos demais para o problema em questão. O objetivo desta dissertação é o desenvolvimento de técnicas especí cas para o casamento de esquemas XML e esquemas relacionais. Tais técnicas exploram as particularidades existentes entre estes esquemas para inferir valores de similaridade entre eles. As técnicas propostas são avaliadas através de experimentos com esquemas do mundo real. / The matching between XML schemas and relational schemas has many applications, such as information integration and data exchange. Typically, schema matching is done manually by domain experts, sometimes using a graphical tool. However, the matching of large schemas is a time consuming and error-prone task. The use of (semi-)automatic schema matching techniques can help the user in nding the correct matches, thereby reducing his labor. The schema matching problem has already been addressed in the literature. Nevertheless, the matching of XML schemas and relational schemas is still an open issue. This comes from the fact that the existing work is whether speci c for schemas designed in the same model, or too generic for the problem in discussion. The mais goal of this dissertation is to develop speci c techniques for the matching of XML schemas and relational schemas. Such techniques exploit the particularities found when analyzing the two schemas together, and use these cues to leverage the matching process. The techniques are evaluated by running experiments with real-world schemas.