A Multi-Faceted Software Reusability Model: The Quintet Web.

Over the past decade, problems in software development and maintenance have increased rapidly. The size of software has grown explosively, complexity of software applications has increased, the nature of software applications has become more critical, and large quantities of software to be maintained have accumulated. During the same time, the productivity of individual software engineers has not improved proportionally. Software reusability is widely believed to be a key to help overcome the ongoing software crisis by improving software productivity and quality. However, the promise of software reusability has not yet been fulfilled. We present a multi-faceted software reusability model, a Quintet Web, that enables designers to reuse software artifacts from all phases. The Quintet Web consists of links of five types of reuse support information among existing document blocks: semantic, horizontal, hierarchical, syntactic, and alternative relationships. The five types of reuse support information are named the Semantic Web, the Horizontal Web, the Vertical Web, the Syntactic Web, and the Alternative Web. The Semantic Web defines the operational functionality of each software block. The Horizontal Web links functionally identical blocks of all phases. The Vertical Web identifies hierarchical relationships of software blocks. The Syntactic Web forms a chain from the declaration of each variable to its uses for all variables. The Alternative Web enables software developers to select an alternative algorithm for an identical functionality. The Quintet Web supports both software development and maintenance. When the Quintet Web is applied to development process, it provides software developers a means to check the consistency of the software being developed. The Quintet Web model is independent of a specific software development method

The use of non-formal information in reverse engineering and software reuse

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Within the field of software maintenance, both reverse engineering and software reuse have been suggested as ways of salvaging some of the investment made in software that is now out of date. One goal that is shared by both reverse engineering and reuse is a desire to be able to redescribe source code, that is to produce higher level descriptions of existing code. The fundamental theme of this thesis is that from a maintenance perspective, source code should be considered primarily as a text. This emphasizes its role as a medium for communication between humans rather than as a medium for human-computer communication. Characteristic of this view is the need to incorporate the analysis of non-formal information, such as comments and identifier names, when developing tools to redescribe code. Many existing tools fail to do this. To justify this text-based view of source code, an investigation into the possible use of non-formal information to index pieces of source code was undertaken. This involved attempting to assign descriptors that represent the code's function to pieces of source code from IBM's CICS project. The results of this investigation support the view that the use of nonformal information can be of practical value in redescribing source code. However, the results fail to suggest that using non-formal information will overcome any of the major difficulties associated with developing tools to redescribe code. This is used to suggest future directions for research

Software test and evaluation study phase I and II : survey and analysis

Issued as Final report, Project no. G-36-661 (continues G-36-636; includes A-2568

Evidentiary treatment of computer-produced material : a reliability based evaluation

Tese de doutoramento em Engenharia Mecânica (Pré-Bolonha), Especialidade de Tecnologia da Produção, apresentada à Faculdade de Ciências e Tecnologia da Universidade de CoimbraCoatings are frequently applied on molds and accessories for the glass industry in order to restrict surface degradation such as oxidation, corrosion, abrasion and wear of the structural material, thereby decreasing the maintenance costs and increasing the lifetime and performance of components. However, in order to obtain accurate lifetime expectancies and performance of the coatings it is necessary to have a complete reliable understanding of their properties. This thesis is on the improvement of the surface properties and integrity of molds, in order to increase their durability, through the application of different types of coatings. Two methodologies were followed to reach such demands: 1 - synthesis, optimization and characterization of coatings currently used in molds surface protection (Ni-based alloys deposited by Plasma Transferred Arc); 2 - synthesis and characterization of new coatings with improved functionalities, deposited by emergent deposition processes such as Atmospheric Plasma Spraying and DC Reactive Magnetron Sputtering. In a first step it was intended to optimize Ni-based coatings deposited by PTA process, studying the effect of substrate dilution on the properties of coatings. In the second part, two different coating systems were evaluated. The first topic investigated the effect of ZrO2 additions on the microstructure, mechanical properties and tribological behavior to Ni-based alloy coatings deposited by APS process, whilst, in the second the influence of V additions on the properties of TiSi(V)N thin films, containing different Si and V contents, deposited by DC reactive magnetron sputtering, was evaluated. The main results to be enhanced are described below for each coating system investigated. The dilution of the substrate showed strongly influence the structure and consequently the hardness, oxidation resistance and tribological behavior of coatings. It was observed that increasing dilution had a detrimental effect on the hardness, oxidation resistance and tribological behavior of coatings at room temperature due to base material incorporation. However, in the latter it demonstrated to have a beneficial effect at high temperature due to the fast formation of oxide layers which protect the coating surface against wear. The post-weld heat treatment performed at coatings reduced the hardness of the partially melted and heat affected zones without affecting the coatings hardness. Furthermore, coatings hardness and wear resistance was increased with annealing treatment. Thus, the best performing coating could only be achieved by, selecting the proper deposition conditions that give the best correlation among mechanical properties, level of oxidation and wear resistance of coatings. ZrO2 additions promoted different impact on the microstructure of a Ni-based alloy, when coatings were deposited using powders mixed by mechanical alloying or using separated powders. A homogeneous and compact microstructure with small zirconia particles evenly distributed in the matrix was obtained in the first case, while a porous microstructure, full of semi-melted Ni powders with large particles of ZrO2 entrapped in their boundaries suggesting a brittle behavior was obtained in the second. In both cases the hardness and wear behavior of ZrO2 rich coatings in relation to the Ni-based one, was improved. However, coatings deposited by powders prepared my mechanical alloying revealed to be much more performing due to their compact structure and even distribution of zirconia. All the APS coatings showed higher hardness values than the Ni-based coatings deposited by PTA, however, their micro-abrasion resistance revealed to be worst, due to the lack of cohesion between powders. The structure of V rich coatings analysed by XRD revealed that V incorporations to the TiSiN system shift the peaks to higher angles, indicating a substitutional solid solution due to the substitution of Ti by smaller V atoms. On the other hand, X-ray diffraction analyses performed at the TiSiN films revealed that the stoichiometric nanocomposite structure for the control of vanadium diffusion was not formed. In fact Si incorporation at the TiN system revealed to shift the diffraction peaks to higher angles, which in combination to the same level of compressive residual stresses measured for all the Si rich films, indicted substitutional solid solution formation. V additions showed successfully increase the hardness and tribological behavior of TiSiVN films. The hardness improvement with V incorporations has shown to be a result of the substitutional solid solution formation, whilst, the improvement of the tribological properties is related to the V2O5 phase formation on the sliding contact that acts as a lubricious tribo-film, which protects the coating from wear. The oxidation resistance of Si and V rich coatings showed to be strongly influenced by their structure. Si and V incorporations at the TiN and TiSiN systems, showed improve and abruptly decrease the oxidation resistance of films, respectively. The oxidation resistance decrease of V rich coatings was attributed to the rapid V ions diffusion throughout the oxide scale, which inhibited the formation of a continuous protective silicon oxide layer, as opposed to TiSiN films case, where a continuous and protective SiO2 layer was built leading to a much lower oxidation weight gain over time. V rich coatings showed lower oxidation resistance than Ni-based coatings PTA, but superior hardness values (some orders of magnitude higher) and greater tribological behavior than PTA and APS deposited coatings.Diferentes tipos de revestimentos são frequentemente aplicados em moldes e acessórios para a indústria do vidro, de forma a atenuar a degradação das suas superfícies, devida às extremas condições de oxidação, corrosão, abrasão e desgaste de uso a que estão sujeitos, diminuindo desta forma os custos de manutenção e aumentando o tempo de vida e o desempenho destes componentes. No entanto, de forma a maximizar o desempenho dos revestimentos, é necessário ter uma completa e fiável compreensão das suas propriedades. Esta tese é totalmente dedicada à melhoria das propriedades da superfície dos moldes, de forma a aumentar a sua durabilidade e performance, através da aplicação de diferentes tipos de revestimentos. No sentido de dar cumprimento a este desafio, duas metodologias foram seguidas: 1 - síntese, optimização e caracterização de revestimentos actualmente usados na protecção da superfície dos moldes (ligas à base de Ni depositadas por PTA (plasma transferred arc)); 2 - síntese e caracterização de novos revestimentos mais resistente e com melhores propriedades, depositados por processos de deposição emergentes no mercado, tal como são os casos do APS (atmospheric plasma spraying) e do PVD (physical vapor deposition). Primeiramente estudou-se o efeito da diluição do material base nas propriedades de uma liga de níquel depositada por PTA usada actualmente na protecção da superfície dos moldes. Na segunda parte diferentes sistemas de revestimento foram avaliados. O primeiro estudo incidiu sobre o efeito da adição de ZrO2 nas propriedades mecânicas, microestrutura e comportamento tribológico de uma liga de Ni depositada por APS, enquanto que o segundo estudo recaiu na análise da influência da adição de V nas propriedades de revestimentos cerâmicos de TiSiN, contendo diferentes teores de Si e V, depositados por PVD. Os principais resultados alcançados durante este trabalho são resumidos seguidamente, para cada um dos sistemas de revestimentos analisados. A diluição do substrato mostrou influenciar a estrutura e consequentemente diminuir a dureza, resistência à oxidação e resistência ao desgaste à temperatura ambiente dos revestimentos. No entanto, teve um efeito benéfico no comportamento tribológico a temperaturas elevadas, devido à rápida formação de uma camada de óxido, que mostrou proteger a superfície contra o desgaste. O tratamento térmico efectuado aos revestimentos após deposição reduziu com sucesso a dureza das zonas termicamente afectada pelo calor e parcialmente fundida, sem alterar a dureza da zona fundida. Além disso, o tratamento de envelhecimento realizado aos revestimentos mostrou aumentar a sua dureza e a sua resistência ao desgaste com a exposição à temperatura. Assim, o revestimento com melhor desempenho só pode ser obtido seleccionando as condições de deposição que originem o melhor compromisso entre propriedades mecânicas, nível de oxidação e de resistência ao desgaste. A adição de zircónia à liga de níquel depositada por APS, usando pós de Ni e ZrO2 misturados por síntese mecânica e pós separados promoveu diferente impacto na microestrutura dos revestimentos. Quando depositados com pós preparados por síntese mecânica, os revestimentos exibiram uma estrutura homogénea e compacta com pequenas partículas de zircónica uniformemente distribuídas al longo da matriz de Ni. Por outro lado, quando depositados separadamente obteve-se uma estrutura extremamente porosa com pós de Ni semi-fundidos e com partículas de ZrO2 aprisionadas na sua interface, sugerindo um comportamento frágil. Independente do procedimento de deposição usado, em ambos os casos a dureza e a resistência ao desgaste dos revestimentos foi melhorada com a adição de ZrO2. Contudo, os revestimentos depositados usando pós produzidos por síntese mecânica revelaram possuir uma maior performance, devido à sua estrutura compacta e distribuição uniforme de ZrO2. Todos os revestimentos depositados por APS revelaram possuir valores de dureza superiores aos revestimentos depositados por PTA, no entanto, a sua resistência à abrasão mostrou ser bastante inferior devido à falta de coesão entre pós. As análises de difracção de raio-X realizadas aos filmes ricos em V revelaram que os picos de difracção se deslocam para ângulos superiores com o aumento do teor em V, indicando a formação de uma solução sólida substitucional. Por outro lado, a análise realizada aos revestimentos de TiSIN revelou que a estrutura estequiométrica nanocompósita, requerida para o controlo da difusão de vanádio não foi formada. De facto, a adição de Si ao sistema TiN revelou também deslocar os picos de difracção para ângulos superiores, o que em combinação com o mesmo nível de tensões residuais medido nos diferentes revestimentos, indica a formação de uma solução sólida substitucional. A Adição de V ao sistema TiSiN mostrou aumentar com sucesso as suas propriedades mecânicas e tribológicas. O aumento da dureza com a adição de vanádio foi atribuído à formação da solução sólida substitucional, enquanto, a melhoria das propriedades tribológicas está relacionada com a formação da fase V2O5, no topo da superfície do filme, a qual age como lubrificante sólido, e portanto protege o revestimento de desgaste. A resistência à oxidação de revestimentos ricos em Si e V mostrou ser fortemente influenciada pela sua estrutura. A adição de Si e V aos sistemas TiN e TiSiN, respectivamente, mostrou aumentar e abruptamente reduzir a resistência à oxidação dos filmes. A diminuição da resistência a oxidação dos revestimentos ricos em V foi atribuída à rápida difusão dos iões de V através da camada de óxido, o que inibiu a formação de uma camada contínua e protectora de óxido de silício, contrariamente ao que acontece nos revestimentos TiSiN, onde uma camada contínua e protectora de Si-O foi formada, levando a menores taxas de ganho de massa devido à oxidação com o tempo. Os filmes ricos em V apresentaram menor resistência à oxidação do que os revestimentos espessos depositados por PTA, no entanto, a sua dureza e resistência ao desgaste mostrou ser bastante superior aos dos revestimentos depositados por PTA e APS

A methodology for integrating legacy systems with the client/server environment

The research is conducted in the area of software methodologies with the emphasis on the integration of legacy systems with the client/server environment. The investigation starts with identifying the characteristics of legacy systems in order to determine the features and technical characteristics required of an integration methodology. A number of existing methodologies are evaluated with respect to their features and technical characteristics in order to derive a synthesis for a generic methodology. This evaluation yields the meta primitives of a generic methodology. The revised spiral model (Boehm,1986; DuPlessis & Vander Wah,1992) is customised to arrive at a software process model which provides a framework for the integration of legacy systems with the client/server environment. The integration methodology is based on this process model.ComputingM. Sc. (Information Systems

On the construction of persistent programming environments

This thesis presents research into the construction of persistent programming systems. Much of the thesis is concerned with the design and implementation of persistent programming languages, in particular PS-algol and Napier. Both languages support machine independent vector and raster graphics data types. Napier provides an environment mechanism that enables the incremental construction and binding of programs. Napier has a powerful type system featuring parametric polymorphism and abstract data types. The machine supporting Napier, the Persistent Abstract Machine, is investigated. The machine supports an efficient implementation of parametric polymorphism and abstract data types. The Persistent Abstract Machine has a layered architecture in which permits experimentation into language implementation and store design. The construction of compilers in a persistent environment is explored. A flexible compiler architecture is developed. With it, a family of compilers may be constructed at relatively little cost. One such compiler is the callable compiler; this is a first class data object in the persistent environment. The uses of such a compiler are explored, in particular in the construction of an object browser. The persistent object browser introduces a new software architecture that permits adaptive programs to be constructed incrementally. This is achieved by writing, compiling and linking new procedures into an executing program. The architecture has been successfully applied to the construction of adaptive databases and bootstrap compilers