[92_PhD_cavalcanti]
Paulo Roma CAVALCANTI.  Criação e manutenção de subdivisões do espaço. [Title in English: The creation and maintainance of space subdivisions]. Ph.D.Thesis. Port. Presentation: 19/03/1992. 140 p. Advisors: Paulo Cezar Pinto de Carvalho e Marcelo Gattass.

Abstract: Geometric Modeling is central to many CAD systems, even though the models traditionally employed do not satisfy all applications. Scientifc applications need to deal with objects made of different materials, with distinct properties. Contact relationships are crucial in kinematics, assembly planning, robotic, and geology. In this context, it is necessary to model aggregates of objects (including solids with lower dimensional parts), keeping track of the adjacency relationships among these objects. This suggests the creation of a development environment where the applications can share not only data but also algorithms that process and transform these data. The way to handle such problems is by supporting arbitrary space subdivisions, instead of the classical subdivision in three regions (interior, boundary, and exterior of a solid object). Planar subdivisions are simpler, but also important, mainly in geology and cartography. The creation of a planar subdivision differs from the creation of a spatial subdivision, specially by the interaction with the user (by the modeling process). The aim of this work is to deal with the problem of creating, combining, and maintaining, in real time, subdivisions of the two- and three-dimensional Euclidean spaces. The main goal is devising a methodology that permits the construction of subdivisions which are topologically and geometrically consistent. This methodology is determined by a modeling process, a mathematical model, and a representation scheme. To achieve this, some extensions were added to the concept of selective geometric complex, creating the basis for a exible scheme that eliminates several restrictions imposed by traditional modeling. The proposed representation scheme maintains an explicit boundary representation and allows one to add boolean operations without any additional restriction (furthermore, it enables the implementation of efficient geometrical algorithms). This provides a powerful set of modeling tools that can be used as the basis for the creation of an interactive construction language for space subdivisions. The construction of basic operations which allow the insertion of a surface patch or a curve segment in a given subdivision in linear time, is also described in detail. This means that a complete subdivision can be built in quadratic time with the number of subdivision's elements.

Abstract: The main purpose of this thesis is to present a methodology of work in Categorical Logics that allows us to write logics in tems of categories and algebras. We present, among other logics, the family of relevant logics which have been used to study computational aspects. This family is showed from the point of view of Categorical Logics. For each logic we present the syntactic systems and discuss their semantics (algebraic and categorical). Finally, we construct formal definitions for categorical and algebraic models. These definitions represent a guide for the construction of new categorical and algebraic models.

1994

[94_MSc_scuri]
Antonio Scaño SCURI. Filtros interativos para imagens digitais no domínio da freqüencia. [Title in English:  Interactive filters for digital images in the frequency domain]. M.Sc. Diss. Port. Presentation: 14/09/1994.  46 p. Advisors: Bruno Feijó and Sidney Paciornik.

Abstract: The widespread use of interactive environments as well as the development of powerful Graphical User Interfaces have made it possible to reach new solutions to old problems. In the field of Digital Image Processing this can be very useful, as for the technique of spatial filtering in the frequency domain. With this technique the Fast Fourier Transform (FFT) of an image is obtained and then edited to preserve or reject specific regions, and then the Inverse Fast Fourier Transform (IFFT) of the edited FFT provides the resulting filtered image. The present work studies the use of interface elements to create graphical masks that function as filters, and proposes the combination of these filters so as to provide great flexibility to the filtering technique. The creation of the filters and the implementation of the FFT algorithms were done in a prototipe of a new image processing system, SPID, which is under development as a platform for Image Processing applications under the Microsoft® Windows™ graphical enviroment.

[94_MSc_duarte]
Carlos Henrique Cabral DUARTE. O desenvolvimento de um compliador MIRANDA usando um método orientado a objectos. [Title in English:  The development of a MIRANDA compiler using an object oriented method]. M.Sc. Diss. Port. Presentation: 29/07/1994.  65 p. Advisor: Roberto Ierusalimschy.

Abstract: The development of functional languages compilers is a complex activity which demands a careful design to avoid the inneficient final product and to allow it to be maintained and extended in a simpler manner.  In this work  we describe the development of a compiler for the Miranda functional language, developed using a method which joins object orientation as a development process approach and formal specification of programming languages as a design technique, changing this activity into a more tractable and  systematic one.

[94_MSc_prates]
Raquel Oliveira PRATES. Visual LED: uma ferramenta interativa para geração de interfaces gráficas. [Title in English: Visual LED: an interactive tool for the generation of graphical interfaces]. M.Sc. Diss. Port. Presentation: 15/08/1994. 58 p. Advisors: Marcelo Gattass and Luiz Henrique Figueiredo.

Abstract: We described and analyzed the design and development of LED interface graphical editor: Visual LED. Visual LED presents to the user three views: textual view, graphical view and a resulting view. The textual and graphical views are editable representations of the same dialog and they are always consistent with each other. The textual view presents the abstract layout of the dialog, in which the user may direct manipulate the elements of the dialog. The user can edit in any of the two views and is also able to switch from one to another, at any moment, without requesting an explicit switch. The resulting view presents the look-and-feel of the dialog. To create Visual LED, we studied the interaction with other generic graphical editors. In the text we discuss these graphical editors and we compare them among themselves and with Visual LED. During the study of these graphical editors, we identified some interaction problems and we present some solutions to them. The major problem identified was the impossibility of editing the hierarchy of a group. For this problem we suggest the solution of the tree, for generic editors and concrete layout interfaces graphical editors, and the hierarchical politics for the layout interfaces graphical editors.

[94_MSc_batista]
Thaís Vasconcelos BATISTA.  Controle de versões no modelo hipermídia de contextos aninhados. [Title in English: Version control in the hipermedia nested context model]. M.Sc Diss. Port. Presentation: 18/03/1994. 109 p. Advisor: Luiz Fernando Gomes Soares. 

Abstract:  The development of Hypermedia Systems requires a conceptual model that offers structures to organize informations and operations for their manipulations. Additionally, that model must have a mechanism for version management in order to reach applications which have to keep in a consistent form, more than one version of the data.  Besides, interoperability and portability have to be possible. So the model must follow an open architecture. The Nested Context Model is a hypermedia conceptual model design based an open architecture, including abstractions for document organization and navigation, versions management and conformance with the MHEG proposal for objects interchange.  This research has three basic objectives.  First, describe the structure proposed by the Nested Context Model and the mechanism to version control.  Following, a notification strategy is proposed to maintain consistency.  Finally, discuss the development of a prototype with version control that implements the concepts introduced by the model in a library of classes.  Over this library, an interface for authoring and navigation was constructed.

1995

[95_MSc hubscher]
Pedro Jorge E. HUBSCHER.  Um processo de desenvolvimento de software usando TALISMAN e MFC. [Title in English: Software development process using TALISMAN and MFC ]. M.Sc. Diss. Port. Presentation: 11/10/1995.  60 p. Advisor: Arndt von Staa.

Abstract: The adoption of operating systems which use a graphical user interface has greatly increased the difficulty in developing software.  New tools have been developed in the effort to counterbalance this increase, however not being successful.  The great deficiency of this tools is that they do not allow the specification of the systems being developed, restricting themselves to the automation of specific tasks.  This text presents a software development process that integrates TALISMAN - an environment for specification and source code composition - the MFC (Microsoft Foundation Classes) library and other auxilary tools. The development process focus on the interface specification, coding and module composition steps.  Represenation languages that permit the combination of specification with high degree of abstraction and source code fragments are employed.  This allows the automatic generaton of source code directly from the specifications.  Specification standards are defined for each objet class used throughout the process.  Automatic "validators", special programs written in TALISMAN's internal language, allow the critics of specification contributing to the increase in quality of the final software.

[95_MSc ridolfi]
Lorenzo Francesco Giovanni Gino Maria RIDOLFI.  Proposta de arquitetura transacional distribuída. [Title in English: A proposal for a distributed transaction architecture]. M.Sc. Diss. Port. Presentation: 26/09/1995.  60 p. Advisors: Marco Antonio Casanova e Luiz Fernando Gomes Soares.

Abstract: This work presents an enhanced architecture for distributed transaction processing with additional mechanisms to assure reliability in information storage.  It is based on the shared-nothing model, and divides server functions into two kinds of nodes, called transaction servers and storage servers, aiming flexibility in data allocation and fault-tolerance.  It also uses a central data communication structure which avoids occurence of faults with complex fixing procedures.  The reliability of this architecture is kept by a recovery and replication mechanism, using the primary-copy replication model, that supports transactions based on their reliability requirements. It offers higher confidence to critical data, while saving resources in ordinary transactions.  Additionally, its replication and recovery mechanism introduces a concept of pesudo-transactions, a transaction with low reliability requirements used to increase the utility of the backup copies, usually poorly used in the primary-copy model.  By doing this, it offers a low cost alternative for application that tolerate a slight data inconsistency.

[95_MSc tocantins]
Claudia de Andrade TOCANTINS.  Armazenamento e manipulação de mapas vetoriais em uma arquitetura palarela. [Title in English: A proposal for a distributed transaction architecture]. M.Sc. Diss. Port. Presentation: 30/08/1995. 120 p. Advisors: Marco Antonio Casanova.

Abstract: Motivated by the need to improve the performance of the execution of spatial operations in geographical database, this dissertation proposes a method to store and manipulate vector maps in a parallel environment.  First, a model for geographic objects and some concepts about vector maps are summarized.  A general architecture for geographic objects management is then presented and some variations for distributed environments are discussed.  Then, the storage structure and its variations are explained in detail.  Procedures to edit the structure and some heuristics to define an uniform load balancing are described.  Finally, some geographic operations are defined and their parallel execution is discussed.

1996

[96_MSc_santos]
André Luiz Soares Clinio dos SANTOS.  VIX - um framework para suporte a objetos visuais. [Title in English: VIX - a framework for supporting visual interactive objects]. M.Sc. Diss. Port. Presentation: 16/12/1996.  66 p. Advisor: Roberto Ierusalimschy.

Abstract: This work presents the modeling and the implementation of a framework which supports visual interactive objects. Its architecture de nes an extensible protocol for constructing new objects and de ning new operations. For the construction of this framework, some requirements were established: extensibility, reuse, portability and conceptual simplicity. These requirements were accomplished. Moreover, the framework has a wide range of applicability for constructing several types of graphical and interactive systems. In order to validate the framework's exibility, a modular system for object direct manipulation, a hierarchical object composer, a graphical editor, and an interface toolkit were constructed. The results obtained from the development of these systems indicate that the framework has accomplished its requirements.

Abstract: This thesis presents a support tool for literate programming. Its development was preceeded by a research of the basic facilites usually required for programs of this class. After that, a framework has been developed to offer those facilites.The framework was developed in standard C++, in such a way that would guarantee its portability. Its efficiency is due to an optimzed kernel which performs all character-level operations, and a well defined application program interface (API) assures its flexibility. On top of this framework an access layer has been created using a configuration language. This layer allows tha, through small programs written in the configuration language, a user can adapt the tool for different literate programming styles, like modular or WWW-enabled documentation.

[96_MSc_muchaluat]
Débora Christina MUCHALUAT.  Browsers e trilhas para documentos hipermidia baseados em modelos com composições aninhadas. [Title in English:  Browsers and trails for hypermedia documents based on nested composition models]. M.Sc. Diss. Port. Presentation: 01/03/1996.  130 p. Advisor: Luiz Fernando Gomes Soares.

Abstract: Navigating in complex hypermedia documents is not an easy task for users, specially when the number of nodes and links is large. In order to improve user orientation during the navigation process, it is necessary to give them global information about the hyperdocument structure and also details about their navigation possibilities at any point in time. These resources are offered by graphic browsers and trails in hypermedia systems. In this work, it is proposed an extension to the fisheye model to build browsers for hypermedia systems that allow nested compositions of nodes. To illustrate the expected results, these tools were implemented for the Nested Context Model in the HyperProp hypermedia system.

[96_MSc_costa]
Fábio Rodrigues COSTA.  Um editor gráfico para definição e exibição do sincronismo de documentos multimídia / hipermídia. [Title in English:  A graphic editor for the definition and exhibition of multimedia/hypermedia documents synchronization]. M.Sc. Diss. Port. Presentation: 23/08/1996.  67 p. Advisor: Luiz Fernando Gomes Soares.

Abstract: Synchronization is an important task in the presentation of hypermedia documents, for that reason hypermedia systems need tools for the definition of temporal and spatial synchronization relationships. This dissertation presents a graphic Editor and Browser (EBS) for temporal and spatial Synchronization of multimedia/hypermedia objects in documents with nested compositions. EBS, part of the HySEE environment (HyperProp Show Editor and Executor), uses the Nested Context Model (NCM) as the structural and presentation model, in conformance with the MHEG standard proposal. The system provides a graphical interface that permits the definition of the temporal and spatial placement of objects, relative either to a time axis or to other objects. It also permits the visualization of the compositions in time and space.

[96_MSc_oliveira]
Jauvane Cavalcante de OLIVEIRA.  TVS: um sistema de videoconferência [Title in English:  TVS: a videoconferecing system]. M.Sc. Diss. Port. Presentation: 15/08/1996.  106 p. Advisor: Luiz Fernando Gomes Soares.

Abstract: This dissertation describes the implementation of a videoconferencing system, the TVS (TeleMídia Videoconferencing System), result of the research done at the TeleMídia Laboratory, part of the Computer Networks and Multimedia Systems Team from the Computer Science Department of the Pontifical Catholic University of Rio de Janeiro, PUC-Rio. TVS is a system that allows the basic transmission of medias such as video and audio in a synchronized and standardized mode. In addition, TVS handles multimedia/hypermedia documents through the Nested Context Model (NCM), according to the MHEG standard proposal. The TVS system supports voting and message sending facilities among participants, in addition to allowing ample environment configuration. The floor control is done by silence detection, in order to improve the interaction among conferees.

[96_MSc_borges]
Renato Ferreira BORGES.  Uma implementação da linguagem School. [Title in English:  An implementation of a compiler for the School object oriented programming language]. M.Sc. Diss. Port. Presentation: 09/08/1996.  70 p. Advisor: Roberto Ierusalimschy.

Abstract: This dissertation presents an implementation of a compiler for he School object oriented language. The work is focused on the specifics compilation techniques employed on this kind of language like message passing, generic types and garbage collection.  At first is introduced a study of many proposals for the implementation of different object oriented languages.  Based on such study, the School compiler is described and evaluated.  In this work, some aspects of modules in object oriented languages are investigated and a proposal is made of a module system for the programming language School.  A formal method is used to describe the module system proposed.

[96_MSc_cerqueira]
Renato Fontoura de Gusmão CERQUEIRA.  Um estudo sobre interoperabilidade entre linguagens orientadas a objetos. [Title in English:  A study on the interoperability of object-oriented languages]. M.Sc. Diss. Port. Presentation: 10/04/1996.  67 p. Advisor: Roberto Ierusalimschy.

Abstract: This dissertation studies some issues related to interoperability of object-oriented languages.  First, it discusses some problems of object-oriented languages that make impossible or very difficult the interoperability among objects defined in different languages and also among distributed objects.  This difficulty harms the goal so disired by object-oriented languages: to develop software components for reuse.  After a discussion about these obstacles, some proposals to solve the interoperability problem are studied, trying to identify their main features.  Finaly, for a better appreciation of some discussed issues, a case study about object model integration is done, where is proposed a mapping between the School language object model and the CORBA standard.

1997

[97_MSc_derraik]
André Luiz Behrensdorf DERRAIK.  Um estudo comparativo de representações de multi-resolução para linhas poligonais. [Title in English: A comparative study of multiresolution representations for polygonal lines]. M.Sc. Diss. Port. Presentation: 25/04/1997.  61 p. Advisors: Marcelo Gattass and Luiz Henrique Figueiredo.

Abstract: This work presents a comparative study of some multiresolution representations for polygonal lines. We study the strip tree, the arc tree and the box tree data structures, comparing their performance for construction, drawing, intersection and selection; and memory storage costs. The comparation uses actual databases available in the Internet. The goal of this study is to identify techniques and algorithms for interactive exploration of large cartographic data bases.

[97_MSc_montenegro]
Anselmo Antunes MONTENEGRO.  Investigação de novos critérios para inserção de pontos em métodos para simplificação de modelos de terreno através de refinamento. [Title in English: Investigation of new insertion methods  for terrain simplification models through refinements]. M.Sc. Diss. Port. Presentation: 27/08/1997.  74 p. Advisors: Marcelo Gattass and Paulo Cezar Pinto Carvalho.

Abstract: In this work we study algorithms for obtaining simplified representations for terrain models. Terrain data is difficult to deal with, due to its complexity and dimension. Simplification methods are one of the techniques used to reduce the natural complexity of real terrain data. Among several simplification methods, greedy insertion with vertical local error measure is the one which has provided best results. In spite of its qualities, the method presents some shortcomings, especially when applied to terrain with different height regions.We investigate the existence of better measures to deal with such problem and propose the adoption of greedy insertion methods in which the local vertical error is modified according to the variability of the surface in a neighborhood of the point under consideration.

[97_MSc_cunha]
Cecília Kremer Vieira da CUNHA.  Planejador de respostas explicativas baseado em uma biblioteca de esquemas RST. [Title in English:  Explanation planner based on a RST scheme library]. M.Sc. Diss. Port. Presentation: 05/05/1997.  110 p. Advisor: Clarisse Sieckenius de Souza.

Abstract: This work presents an explanation planner which objective is to close to an end-user the knowledge applied in a knowledge based system. This disclosure is possible specially due to the generation of natural language explanations, which provide rhetorical structure and organization to the information presented.  Other forms of expression can also be planned, among which the use of graphic resources is currently available.  One of the main contributions of this work is the application of knowledge in Semiotics and Computational Semiotics to the construction of a solution, briging a new perspective to approach the usability challenge.  The planner here proposed has been devloped for a real knowledge based system in a project of ADDLabs.

[97_MSc_szenberg]
Flávio SZENBERG.  Um algoritmo para visualização de terrenos com objetos. [Title in English:  An algorithm for the visualization of terrains with objects]. M.Sc. Diss. Port. Presentation: 27/08/1997.  58 p. Advisor: Marcelo Gattass and Paulo Cezar Pinto Carvalho.

Abstract: This work describes a method for the visualization of terrains and objects by means of the combination of two algorithms, one for terrains and one for objects. Our purpose is to generate, effective and quickly, aerial images of a terrain with objects as houses, vehicles and transmission lines and like this to allow a simulate flight. For the objects, described by lines and polygons, the algorithm of Z-Buffer is used; for the terrain, described through maps of heights, the algorithm of improved release of rays is used, called algorithm of Flotation Horizon.

[97_PhD_souzafilho]
Guido Lemos SOUZA FILHO.  Sincronismo na modelagem e execução de apresentações de documentos multimídia. [Title in English:  Synchronism in the modeling and execution of multimedia documents presentation]. Ph.D. Thesis. Port. Presentation: 29/09/1997.  221 p. Advisor: Luiz Fernando Gomes Soares.

Abstract: Logical, temporal and semantic complexity of multimedia and hypermedia documents claims for a conceptual model permitting its specification and manipulation. Expression of ideas through documents presupposes a logical ordering of information fragments represented through different media. This ordering defines the time and space occupied by the presentation of each component. This work proposes a multimedia document conceptual model called Nested Context Model (NCM). When this work started, NCM had been object of other studies focused on structural aspects of documents. So, the main contribution of this thesis was to propose entities allowing to capture specifications of temporal and spatial synchronism in order to define documents structured as nested compositions. The specification of the presentation’s temporal synchronism is based in two entities: events and links. The occurrence of a collection of events aligned in time by links defines the semantic of documents’ presentations. Spatial synchronism specification is captured by an entity called descriptor, which keeps the specification of the presentation characteristics separated from the data to be presented. This facility allows the definition of alternative presentations for documents as well as for its components. In order to validate the proposed model, tools allowing the edition and execution of NCM documents presentations were developed.

[97_PhD_seixas]
Roberto Beauclair SEIXAS.  Visualização volumétrica com ray-casting num ambiente distribuído. [Title in English: Ray-casting volumetric visualization in a distributed computer environment]. Ph.D. Thesis. Port. Presentation: 09/04/1997.  52 p. Advisor: Marcelo Gattass and Paulo Cezar Pinto Carvalho.

Abstract: Ray-Casting is a useful volume visualization technique applied to medical images such as computer tomography (CT) and magnetic resonance image (MRI). It has, however, a high computational cost that results in a slow rendering process, which compromises the interactivity that is necessary for a good comprehension of the three-dimensional data set. This work proposes optimization strategies to the ray-casting algorithm to improve its efficiency. To enhance, even further, the thesis investigates the use of a distributed computer environment through a communication protocol between heterogeneous and nondedicate LAN-connected workstations. The ideas proposed here were implemented in two versions of the algorithm, one sequential and one parallel. Test results, obtained with these implementations and real data sets, show that it is possible to obtain interactive time with the current available machines.

[97_MSc_rodrigues]
Rogério Ferreira RODRIGUES.  Formatação temporal e espacial no sistema HyperProp. [Title in English: Temporal and spatial formating mechanism in the HyperProp system]. M.Sc. Diss. Port. Presentation: 12/05/1997.  108 p. Advisor: Luiz Fernando Gomes Soares.

Abstract: Multimedia/hypermedia systems development requires an element responsible for receiving a document presentation specification and to execute its exhibition to the user. The main tasks of this element, called temporal and spatial formatter, are the generation and the maintainance of an execution plan, the control of the presentation of the document’s components, and the allocation of resources for media presentation. This dissertation presents the spatial and temporal formating mechanisms implemented in the HyperProp system, besides the formatter’s interfaces with other parts of the system.

1998

[98_MSc_ferreira]
Carla Cristina Fonseca FERREIRA.  Um estudo sobre arquivos vetoriais para visualização de mapas na Web. [Title in English: A study on vectorial files towards map visualization in the Web]. M.Sc. Diss. Port. Presentation: 11/05/1998. 84 p. Advisor: Marcelo Gattass and Luiz Henrique Figueiredo.

Abstract: This paper presents a study on the transmission of maps in the World Wide Web. Maps are approximate representations of the Earth surface in which points of the globe are projected on a plane. An important feature of figures that represent maps is that they have polygonal lines with a large number of points. With current vector formats these points generate archives that are too large to be transmitted through the web. The use of image formats, although common in the web today, only provide poor resolution figures that do not scale well. A review of current metafile formats is presented, followed by a study on compression algorithms. The thesis proposes strategies to reduce the size of the archives by restricting the precision of the points, eliminating repeated points and performing an efficient coding of the coordinates. Real examples are shown to evaluate the proposed strategies and recommendations are made based on these examples.

[98_PhD_martins]
Isa Haro MARTINS.  Um instrumento de análise semiótica para linguagens visuais de interfaces. [Title in English: A semiotic analysis instrument tool for interface visual languages]. Ph.D. Thesis. Port. Presentation: 24/04/1998. 266 p. Advisor: Clarisse Sieckenius de Souza.

Abstract: Geometric Modeling Systems have changed from textual batch data entry styles to direct manipulation graphical interface data entry, as a consequence of advances in hardware technology. This has brought out several advantages to users. However, it has also raised several issues that remain to be resolved, with respect to the use of visual resources as expressive tools. One of the weakest points is the non-systematic use of the expressive resources in interactive language specification. This problem is particularly important in Geometric Modeling Systems, due to the complexity of such systems and the language constraints imposed by visual expression. These systems are representation/abstraction of physical world objects, so, they are intrinsically semiotic systems. Because they are signs generating systems, they have to support users in the fundamental actions related to this task: (a) to select and to establish significant shapes (primary and secondary) and (b) to supply systematic procedures for the interpretation of such shapes when used in communication/representation acts. This work discusses the use of direct manipulation visual languages in Geometric Modeling Systems through the use of a semiotic paradigm. It proposes a systematic analysis to the use of visual expressive resources and shows the effect of this approach in interface specification environments. The work analyses the limits of the visual resource as an expressive medium and its structuring as a language. Based on the theoretical directives presented, it proposes an extension of TAG (Task-Action Grammars), including semiotic aspects of the language, named Semiotic TAG (STAG). The STAG reflects the systematization of expressive choices, in order to support designers in the specification of these particular visual languages. It acts together with orientation directives for coding the visual language (ODCVL) and with evaluation heuristics of the visual language (EHVL). Finally, an environment for the implementation of STAG together with the ODCVL and EHVL is proposed.

[98_MSc_rosseti]
Isabel Cristina Mello ROSSETI.  Uma biblioteca para balanceamento de carga em ambiente distribuídos. [Title in English: A load balancing library developed for a distributed environment]. M.Sc. Diss. Port. Presentation: 05/03/1998. 111 p. Advisor: Noemi de La Roque Rodrigues.

Abstract: Many load balancing techniques have been proposed, in order to improve the performance of parallel applications. This dissertation presents some existing load balancing algorithms.  These algorithms are presented according to an analytical model called Matrix Interactive Model.  The application of some of these algorithms to a specific problem, the N-body problem, is discussed.  A load balancing library developed for a parallel implementaion of this problem, based on Barne-Hut algorithm, is also discussed.

[98_PhD_leite]
Jair Cavalcanti LEITE.  Modelos e formalismos para a engenharia de semiótica de interface de usuários. [Title in English: Models and formalisms for the semiotic engineering of user interfaces]. Ph.D.Thesis. Port. Presentation: 07/10/1998. 205 p. Advisor: Clarisse Sieckenius de Souza.

Abstract: Interactive systems usability could be enhanced if users learn all the knowledge - the usabilty model - that capability them in applying designer’s potential solutions to domain tasks. The Semiotic Engineering approach perceives interactive systems as metacommunication artifacts that send a message from designer to users whose expression is the lower-level messages exchanged between user and system and whose content is the usability model. Starting from this perspective and based on semiotic theory concepts from Charles S. Peirce and Umberto Eco we present conceptual models to the interface as the expression and to the usability model as the content of designer’s message. We also develop a semiotic system to support user interface design. The system is composed by a specification language and rules that maps specified messagens to user interface widgets. Our emphasis here is not in aesthetics aspects of user interfaces, but in the interactive and performing nature of the interface message as it is carried throughout the computational medium.

[98_MSc_huang]
Juli Ling Ching HUANG.  Uma arquitetura para o desenvolvimento de interfaces gráficas baseada em grafos. [Title in English: An architecture for the development of graphical interfaces based on graphs]. M.Sc. Diss. Port. Presentation: 21/08/1998. 111 p. Advisor: Marcelo Gattass and Waldemar Celes.

Abstract: The development of graphical interfaces based on the direct manipulation of application objects on a canvas is a complex task that finds little support in nowaday’s programming technology. Directed graphs in the form of schematic diagrams are used in programs for supervision, control and simulation of electric power systems, industrial plants, and many other similar systems in which the process flows through a net of components. Due to the large number of applications based on these types of objects, they have come to deserve specialized tools for their development. The present work proposes an architecture for the development of graphical interfaces based on graphs, it allows users to create and to instance equipments with attributes and behavior that depend on the application, with a high level of abstraction. As a tool for the development of applications based on the proposed architecture, a graphical object library with support for the underlying graph, was implemented. The goal of this architecture is to allow the programmer to focus on the application’s development rather than on user interface issues. The proposed architecture was used in industrials applications prototypes in order to validate the ideas presented here.

[98_PhD_coelho]
Luiz Cristovão Gomes COELHO.  Modelagem de cascas com interseções paraméricas. [Title in English: Modeling finite-element meshes with parametric intersections]. Ph.D. Thesis. Port. Presentation: 14/11/1998. 94 p. Advisor: Marcelo Gattass and Luiz Henrique Figueiredo.

Abstract: We present a methodology for modeling finite-element meshes defined on parametric surface patches. The idea is to build curves and generate meshes over the parametric patches built with these curves, which also connect adjacent meshes. The final model is a representation of all meshes combined into a single data structure. The basic tools to generate such meshes are the user interface to model space curves and the geometric algorithms to construct the elementary domain mappings. The main problem in composite modeling is how to handle mesh surfaces that intersect each other. We present an algorithm that models the intersection curves precisely and adjusts both meshes to the newly formed borders. The algorithm is part of an interactive shell modeling program, which has been used in the design of large offshore oil structures. We avoid unacceptable interaction delays by using a variant of the DCEL data structure that stores topological entities in spatial indexing trees instead of linked lists. These trees speed up the intersection computations required to determine points of the trimming curves, and also allows mesh reconstruction using only local queries.

[98_PhD_prates]
Raquel Oliveira PRATES. A engenharia semiótica de linguagens de interface multi-usuário. [Title in English: The semiotic engineering of multi-user interface languages]. Ph.D.Thesis. Port. Presentation: /10/1998. 117 p. Advisor: Clarisse Sieckenius de Souza.

Abstract: Nowadays there are guidelines, frameworks, models and toolkits that support the development of multi-user interfaces. Toolkits assist designers in buiding the interface, whereas guidelines and frameworks direct the designer towards issues to be considered during interface design. Models, on their turn, allow for the description of the conceptual model of the group (or part of it) to be represented in the interface. Nevertheless, none of these provide the designer with an environment in which to plan and define the system’s interface. We take a Semiotic Engineering approach, in which the interface is perceived as a one-shot message being sent from the designer to the users. In particular, interfaces can be viewed as meta-communication artifacts, since they can also exchange messages with the users. Furthermore, in multi-user environments, they are also communication embedding artifacts, since they allow for the communication among users. This approach focuses on the expression of the designer and requires the development of means to support this expression. In this work, we intend to provide support to  multi-user interface designers, in a Semiotic Engineering framework. In order to meet our goal, we developed a meta-communication model from which models and techniques to support the development of multi-user interfaces can be developed. The meta-communication model proposes that designers should be provided not only with means to describe their messages, but also some qualitative indications on their description. Based on this model, we developed a model of an architecture to support the design of multi-user interfaces. This model assists designers that develop multi-user interfaces top-down. Therefore, this work is the first step in the direction of an environment to support the design of multi-user interfaces with quality.

[98_MSc_choren]
Ricardo CHOREN Noya.  Quest - um sistema de avaliação educacional para a Web. [Title in English: Quest - an  educational assessment system to the Web]. M.Sc. Diss. Port. Presentation: 12/03/1998. 111 p. Advisor: Hugo Fuks.

Abstract: The Internet has a great potential for educational purposes. In 1997, the Software Engineering Laboratory at PUC-Rio implemented a first version of AulaNet™ , a web-based educational environment. This year, some of the teaching staff will be using this environment to offer regular term disciplines through the Web. This work introduces Quest, the quiz generator and assessment tool incorporated into AulaNet™ to provide the means to support educational assessment through the Web.

1999

[99_MSc_cusatis1] [99_MSc_cusatis2]
Affonso CUSATIS JUNIOR.  Ray casting intervalar de superfícies implícitas com aritméticas afim. [Title in English: Interval ray casting for implicit surfaces with affine arithmetics]. M.Sc. Diss. Port. Presentation: 23/04/1999. 67 p. Advisor: Marcelo Gattass and Luiz Henrique Figueiredo. .

Abstract: This work investigates ray casting, the most natural visualization technique for implicit surfaces, using interval methods. Some robust algorithms are implemented for ray casting generic surfaces, using interval methods and conventional numerical methods in the determination of ray-surface intersections – a central operation in ray casting – and a new interval calculation model is tested: affine arithmetic (AA), proposed as a alternative for standard interval arithmetic (IA). AA was designed in order to avoid the IA’s error explosion problem at long interval calculation sequences, and takes into account correlations between terms in a interval expression. So, AA defines more expensive operations but yields more precise results, and this feature may accelerate several interval algorithms.

[99_MSc_ferreira]
Alexandre Guimarães FERREIRA. Uma arquitetura para a visualização distribuída de ambientes virtuais. [Title in English: An architecture for the distributed visualization of virtual environments]. M.Sc. Diss. Port. Presentation: 05/05/1999. 83 p. Advisor: Marcelo Gattass and Waldemar Celes Filho.

Abstract: A number of applications require a visualization system that provides multiple visions of an animated virtual environment. The disposal of multiple visualization devices around a user consists in a natural solution to compose a panoramic view of the scene. Virtual environment panoramic views, simultaneously supplied to different users, can be obtained from different points of view, in a more sophisticated arrangement. Each panoramic scene presented to a user is formed by the composition of images generated in each visualization surface. This way, it is possible to imagine each visualization device as a window to the virtual environment. The use of this technology seeks to enhance human perception and to increase users' immersion. This is reached through a quantitative increase of the visual stimuli provided, due to the use of multiple windows. A traditional approach for the development of such system is based on specialized systems that use dedicated hardware, which is responsible for the visualization devices’ centralized processing and control. This work proposes a distributed architecture to be used in heterogeneous networks with low-cost graphic workstations, seeking to provide greater scalability, portability and flexibility to the visualization system. The proposed architecture seeks to support the development of applications that present a consistent visual outcome for the virtual environment. To accomplish that, techniques are presented to assure synchronism and integrity among several workstations.

[99_MSc_gomes]
Antonio Tadeu Azevedo GOMES. Um framework para provisão de QoS em ambientes genéricos de processamento e comunicação. [Title in English: A framework for QoS provision in processing and communication generic domains]. M.Sc. Diss. Port. Presentation: 31/05/1999. 152 p. Advisor: Luiz Fernando Gomes Soares.

Abstract: Over the past few years, an emerging demand for multimedia communication and processing systems has been observed. On these systems, the notion of quality of service (QoS) has evolved rapidly, either as a way for user requirements specification, or as a reference for the configuration, operation and maintenance of the resource sharing and orchestrating mechanisms. This thesis is motivated by the belief that architectures for the provision of specific services are not flexible enough to support new media treatment technics. As an alternative, the thesis presents a framework that organizes QoS provision in a domain which is sufficiently generic to include any communication and processing environment, encompassing from specific subsystems to distributed multimedia systems. With these characteristics, the framework allows the construction of configurable systems, with regard to the introduction of new services, and eases the implementation of resource sharing and orchestrating mechanisms.

[99_MSc_gonzalez]
Esteban Walter GONZALEZ CLUA. Modelagem procedimental de elementos da natureza. [Title in English: Procedural modeling of natural phenomena]. M.Sc. Diss. Port. Presentation: /12/1999. 96 p. Advisor: Marcelo Gattass and Marcelo Dreux.

Abstract: Modeling natural phenomena is an area of active research and growing importance in Computer Graphics. The purposes of this work are to present a thorough bibliography about this subject, to cover fundamental concepts and to propose some new techniques. It focuses mainly on the procedural modeling techniques but it also present specific visualization and ilumination methods.

[99_MSc_fortunato]
Luidi Xavier FORTUNATO. 2BuyNet - um framework para instanciação e administração de lojas para a Internet. [Title in English: A framework for instantiation and administration of Web stores]. M.Sc. Diss. Port. Presentation: /04/1999. 103 p. Advisor: Carlos José Pereira de Lucena.

Abstract: This dissertation presents a software development approach for the construction of electronic commerce websites. At first, problems and features related to the domain application are discussed. The dissertation also presents some existing software tools for webstore creation, their proposed solutions and the approach they use to implement their features. Based on these comparisions we have developed a framework called 2BuyNet. The framework constitures an original software engineering approach for the development of electronic commerce sites. This dissertation describes the design rationale for the framework structure, as well its pros and cons. As an exercise of the use of the framework an application also called 2BuyNet has been instantiated, using the Web as the interface. This application has been published on the Internet and works both as a web store generator service and a web store administrative tool.

[99_MSc_rodrigues]
Marcus Antonio Almeida RODRIGUES. Um framework para a provisão de serviço de multicast em ambientes genéricos de comunicaçao de dados. [Title in English: A framework for the provision of multicast service in data communication generic domains]. M.Sc. Diss. Port. Presentation: 21/05/1999. 135 p. Advisor: Luiz Fernando Gomes Soares.

Abstract: Since most of the solutions available as candidates to the implementation of a multicast service have been designed to fit specific infrastructure conditions or service characteristics to which they are aimed, or, still, to fit management politics for user groups, the present work introduces a framework for designing a multicast service whose main features are its generality and independence toward possible communication systems and applications. This framework allows the implementation of specific multicast services in a fast and organized way, by reusing the whole generic structure presented, in addition to the configuration of some service components. The framework consists of two basic services: a group management service, and a support service to the construction of the multicast distribution infrastructure. Its use is illustrated by the implementation of broker agent for centralized group communication, applied to a video distribution service.

[99_PhD_fontoura]
Marcus Felipe Montenegro Carvalho da FONTOURA.  Uma abordagem sistemática do desenvolvimento de frameworks. [Title in English: A systematic approach to framework development]. Ph.D.Thesis. Eng. Presentation: 05/07/1999. 156 p. Advisor: Carlos José Pereira de Lucena.

Abstract: This work proposes a design language that represents the frameworks hot-spots and its instantiation process as first-class citizens. The language is defined as an extension to UML. Knowledge-based transformational tools are described to illustrate how the proposed design language can be used to automate several steps of a framework development process: design, implementation, instantiation, and maintenance. The semantics of the language is formally presented to enhance its understanding by a wide variety of users and to allow for the construction of new supporting tools. A consequence of this formalization is a precise definition of what frameworks really are. Several case studies are presented to illustrate the use of the approach in real-world framework development scenarios.

[99_MSc_frederick]
Paula FREDERICK. Visualização eficiente de objetos gráficos. [Title in English: Efficient visualization of graphical objects]. M.Sc. Diss. Port. Presentation: 01/07/1999. 103 p. Advisor: Marcelo Gattass.

Abstract: This work presents a study on the efficient visualization of large figures, such as maps and CAD drawings. These large figures are usually formed by a great number of graphical objects, generally most of them being polygonal lines with many points. In Computer Graphics, conventional techniques for drawing graphical objects are unable to offer interaction times when applied to a huge data volume. Thus, it is necessary to use appropriate mechanisms for speeding up this process. A brief description of graphical objects and of spatial access methods is made. Then some methods are proposed for storing and efficiently retrieving sets of twodimensional graphical objects in a secondary storage media. These methods consist in using persistent data structures composed by an R-tree, V-trees, and Quadtrees. In order to demonstrate the efficiency of the proposed solutions, some experiments done with real geographic data are shown.

[99_MSc_oliveirajunior]
Pedro Paulo de Magalhães OLIVEIRA JÚNIOR.  Exames virtuais utilizando um algoritmo de ray casting acelerado. [Title in English: Virtual exams using a ray casting accelerated algorithm]. M.Sc. Diss. Port. Presentation: 07/12/1999. 64 p. Advisor: Marcelo Gattass.

Abstract: This work presents a study on virtual exams, which are techniques for visualizing the inner part of the human body using volume visualization techniques for clinical evaluation purposes. The virtual exams aim at being an alternative for conventional digestive endoscopy, colonoscopy, and bronchoscopy exams. We present a comparative study between virtual exams and their analogue conventional exams, analyzing advantages and disadvantages of each of the techniques. We also propose an algorithm for accelerating volume visualization with ray casting, and compare the results obtained with other optimization techniques.

[99_PhD_colcher]
Sergio COLCHER.  Um meta modelo para aplicações e serviços de comunicação adaptáveis com qualidade de serviço. [Title in English: A meta model to adaptable communication services and applications with service quality]. Ph.D.Thesis. Port. Presentation: 22/11/1999. 114 p. Advisor: Luiz Fernando Gomes Soares.

Abstract: One of the main chalenges posed to the telecommunications services operators is to develop a single infrastructure to support the integration of a wide range of services and to allow for the rapid creation, alteration and continuous adaptation of these services to new evolving conditions or demands. The variety of requirements and the rapid evolving technology impose many difficulties, specially when the goal is to develop services based on a limited number of pre-defined options. This work presents a model in which communication services platforms will be constructed to support some kind of adaptability in order to meet the wide range of different demands, the presence of run-time changes in applications requirements and the rapid evolving technology. The model provides some basic abstractions for the representation of multicasting and Quality of Service (QoS) within multimedia communication services and is based on the pipes-and-filters architectural style. Pipes correspond to the explicit representation of connections between components (the filters) that, in turn, represent the active processing elements of a service implementation. QoS specifications can be asscociated to pipes, which are then called MediaPipes. MediaPipes correspond to an abstract programming entity for the QoS treatment and also allow for the exposure of internal implementation details whenever adaptations are necessary.

[99_PhD_barbosa]
Simone Diniz Junqueira BARBOSA.  Programação via interfaces. [Title in English: Programming via interface]. Ph.D.Thesis. Port. Presentation: 23/12/1999. 109 p. Advisor: Clarisse Sieckenius de Souza.

Abstract: In the past few years, we have witnessed an increase in software functionality as an attempt to meet most users’ needs. This approach brings about serious usability challenges, due to an increase in application complexity as well. In order to try and meet users’ needs, without overloading the application with functionality that is rarely used, there is a tendency to allow end users to configure or program applications, by means of mechanisms that support the so-called end user programming. However, many existing techniques fail to attain acceptable thresholds of usefulness and usability. This work addresses some of the challenges posed by extensible applications. We follow an approach that drops some walls between interface and extension. This approach brings some extension mechanisms to the interface, and readily accessible to end-users, namely extensions based on the semantic–pragmatic resources of metaphors and metonymies. These mechanisms were chosen due to the acknowledgment of the Cognitive Sciences of their critical role in our reasoning processes, especially when we try to describe or understand complex or abstract concepts. We describe an extensible application model that makes use of a knowledge base in which we represent the domain and application elements that may be extended, as well as the necessary classifications for calculating the possible extensions. Our model takes into account the communicative aspects of computer applications, and follows Semiotic Engineering principles to guarantee the consistency between the original application and the extended one. For that purpose, our model entails the representation of rules that constrain interface amendments, so that extended functionality is adequately reflected at the resulting interface.

2000

[00_PhD_garcia]
Alex de Vasconcellos GARCIA.  Um modelo categórico para traduções entre linguagens de programação. [Title in English: A categorical model for translating programming languages]. Ph.D. Thesis. Port. Presentation: 26/05/2000. 135 p. Advisor: Hermann Edward Haeusler.

Abstract: This thesis proposes a categorical model for translating programming languages.  This model is used to establish a formal condition that a translation should satisfy in order to preserve program maintainability throughout the translation process.  For this purpose, we start from a categorical model proposed by R.F.C. Walters for context-free languages.  In order to establish the criterion for preserving maintanability, it was necessary to introduce semantics for the categorical models of context-free languages.  The examples shown illustrate that the arrow semantics (arrows are models of derivation pieces) is related to the preservation of program maintainability. We believe that the technique we developed, not only applies to the problem studied in this thesis, but also brings an important insight regarding the semantics of programming languages and the way in which the programmer's intention is related to the syntactical structure of a program.

[00_PhD_schmidt]
Ana Elisa Ferreira SCHMIDT.  Visualização tridimensional de dados volumétricos e modelos poligonais usando o algoritmo Shear-Warp. [Title in English: Tridimensional visualization of volumetric data and polygonal models using the Shear-Warp algorithm]. Ph.D. Thesis. Port. Presentation: 28/04/2000. 109 p. Advisor: Marcelo Gattass and Paulo Cezar Pinto Carvalho.

Abstract: This thesis presents a study on the integration between Shear-Warp and Z-Buffer algorithms, and extends the Shear-Warp algorithm to handle scenes composed of both volume and polygonal data. Shear-Warp techniques provide an efficient way to perform the projection and blending stages of the volume-rendering process. They treat volume-data slices in a coherent order and can be naturally integrated with the Z-Buffer algorithm. We present methods to handle opaque/translucent volumes combined with opaque/translucent polygonal models. As volume data usually has a different resolution from that of the final image, in which Z-Buffer renders the polygonal data, several variants for this integration that try to reduce aliasing problems are analyzed. Results are shown to support some conclusions on the trade-off quality- versus-time that can be expected.

[00_MSc_moura]
Ana Lúcia de MOURA.  Um ambiente de suporte à adaptação dinâmica de aplicações distribuídas. [Title in English: An environment to support dynamic adaptation of distributed applications]. M.Sc. Diss. Port. Presentation: 28/09/2000. 88 p. Advisor: Noemi de La Rocque Rodrigues.

Abstract: Component-based programming is presently an important trend for the development of distributed applications, allowing complex systems to be constructed by combining several independent and reusable components.  These components implement specific services accessed through interfaces that traditionally define only functional requirements - such as operations signatures - and abstract the non-functional properties of the offered services, such as performance, security or availability.  However, the increasing demand for distributed applications that are able to meet non-functional requirements like the ones listed above, and the dynamic behavior presented by the execution environment of these applications, impose that not only middleware platforms, but also applications, dinamically adapt to the state of their execution environment.  For that to be possible, it is essential that the application be able to handle the non-functional properties of the services provided by their components. The purpose of this work is to offer an environment that supports dynamic adaptation of distributed applications to variations in the non-functional properties of the services provided by their components.  For that we developed facilities and mechanisms that allow applications to dinamically select the components that best suit their requirements, verify if these requirements are being met, when appropriate, to variations in the non-functional properties of the services in use.

Abstract: Based on the study of different electronic commerce software applications and principally inspired by the research work and software evolution carried out in the Vmarket framework, this dissertation presents the Commercepipe Object Oriented Framework as an alternative for the instantiation of Consumer to Business Virtual Markets on the Internet. Using Software Agents Technology combined with the WAP (Wireless Application Protocol) as a wireless interface to access Internet services, the framework proposes a new approach for C2B markets, bringing a new vision of how sellers and buyers can interact to realise commercial transactions through the Internet.

[00_MSc_muniz]
Bruno Cavalcanti MUNIZ.  Notificação e controle de versões para o suporte à autoria cooperativa no sistema HyperProp. [Title in English: Version notification and control to support authoring in the HyperProp system]. M.Sc. Diss. Port. Presentation: 28/08/2000. 115 p. Advisor: Luiz Fernando Gomes Soares.

Abstract:  It is important to a hypermedia authoring system to support simultaneous document editing, done by several authors, in an adequate and efficient way. To accomplish that, hypermedia systems incorporate version control mechanisms integrated to notification schemes, which inform authors about significant events related to creation and editing of versions. This work specifies notification control mechanisms for the Nested Context Model (NCM), which were implemented within the hypermedia authoring system HyperProp. It is important to observe that these mechanisms can be adapted to other hypermedia models based on compositions and offering version control functionalities. In addition, an implementation of the NCM version control is also presented, enabling, among other facilities, the graphical visualization of hyperdocuments history in the HyperProp system.

[00_MSc_martins]
Carlos Bazílio Martins.  Detecção de paralelismo a partir de semântica denotacional e grafos de dependência. [Title in English: Parallelism detection based on denotational semantics and dependency graphs]. M.Sc. Diss. Port. Presentation: 16/06/2000. 103 p. Advisor: Edward Hermann Haeusler.

Abstract: This work proposes a generic architecture that generates parallel automatic code from sequential programs. In literature this subject is called implicit parallelism. The architecture has a target language’s denotational semantic specification and an example code in such a language as its input. The output is a parallel code in the same abstraction level as the original sequential code. Intermediate code generation with parallel constructs (cobegin/coend, forall, ...) is one of the intermediate steps. This code is processed to be instantiated to a particular machine. Our implemented prototype processes the C language and generates multithreaded programs from sequential ones.

[00_PhD_cassino]
Carlos Roberto Serra Pinto CASSINO.  Distribuicão de carga de sistemas Web controlada por ferramentas de construção de páginas dinâmicas. [Title in English: Web systems load distribution controlled by dynamic page construction tools]. Ph.D. Thesis. Port. Presentation: 19/12/2000. 81 p. Advisor: Roberto Ierusalimschy.

Abstract: Load distribution among several servers is a scalability solution typically adopted in Web sites. E-commerce applications, among others, use dynamic pages to offer sophisticated services, demanding even more processing power from those servers. This sophistication imposes some constraints to the load distribution mechanism, such as fixing some clients on some servers, diminishing the performance of the distribution. Our thesis is that integrating the load distribution control into the dynamic page construction tool allows the use of internal information of the tool, and therefore a more effective control of the distribution and more efficiency. In this work, we propose a load distribution model in which the page construction tool controls, by manipulating the embedded links of the generated pages, the distribution of the clients among the servers. Since this load distribution model differs from other existing models, a relevant part of our work is the implementation and analysis of a prototype.With this prototype, we could analyze the performance of some load sharing algorithms, the behavior under overloads, and others. This analysis shows that this distribution model achieves a good performance when compared to others models commonly adopted. Moreover, this integrating model is able to handle the constraints imposed by the dynamic applications, such as client fixing and distribution guided by classes of requests.

[00_MSc_mesquita]
Fernanda Victal MESQUITA.  Suporte ao desenvolvimento de aplicações SPMD. [Title in English: Support to the development of SPMD applications]. M.Sc. Diss. Port. Presentation: 07/01/2000. 57 p. Advisor: Noemi da La Roque Rodrigues.

Abstract: This work describes the implementationof a prototype of SAMBA (Single Program Multiple Balancing).  SAMBA is a tool that supports the development of SPMD parallel programs.  It is basically intended for applications where the execution of each task is totally independent of the others.  SAMBA also supplies a library of load balancing algorithms to manage the distribuition of the workload between the parallel processes.

[00_MSc_amaral]
Fernando Náufel AMARAL.  RETOOL: uma lógica de ações para sistemas de transição temporizados. [Title in English: RETOOL: an action logic for time transition systems]. M.Sc. Diss. Port. Presentation: 09/05/2000. 117 p. Advisor: Edward Hermann Haeusler.

Abstract: This dissertation defines RETOOL, an action logic featuring an operator to denote necessary conditions and postconditions of actions in a timed transition system (an extension of the formalism of transition systems meant to model real-time reactive/concurrent computational systems). A semantics for RETOOL is presented and compared to previous proposals. An adequate axiomatization is given, along with detailed correctness and weak completeness proofs.

[00_MSc_rodrigues]
Leandro Marques RODRIGUES.  Integração de documentos SMIL ao sistema HyperProp e desenvolvimento de ferramentas para exibição de objetos com relacionamentos de sincronização. [Title in English: Integration of SMIL document with the HyperProp system and the development of tools for object presentation with synchronization relations]. M.Sc. Diss. Port. Presentation: 21/11/2000. 118 p. Advisor: Luiz Fernando Gomes Soares.

Abstract: The use of the World-Wide Web to distribute multimedia documents with temporal and spatial synchronization relationships is a research topic that has recently gained a lot of attention. The SMIL language had its recommendation published by the W3C for declarative authoring of these documents, but it has some limitations. In order to overcome these limitations, this dissertation presents the integration of SMIL documents with HyperProp, a hypermedia system based on a conceptual model called NCM (Nested Context Model). This integration allows SMIL documents to be refined with NCM facilities and manipulated in a hypermedia system with version control and high-level authoring tools. The dissertation also proposes some extensions to NCM, adding some concepts found in SMIL, in order to simplify the authoring of NCM documents with temporal synchronization relations. Finally, the dissertation presents the development of presentation tools, integrated with the HyperProp system, to control the presentation of continuous media (audio and video) and static images, supporting all temporal and spatial relations defined in the NCM model, besides user interaction relations.

[00_PhD_moura]
Leonardo Mendonça de MOURA.  Análise e verificação de programas. [Title in English: Program analysis and verification]. Ph.D. Thesis. Port. Presentation: /02/2000. 199 p. Advisor: Carlos José Pereira de Lucena.

Abstract: Presently, program analysis and verification is at best achieved by a hand-crafted tool specific to a programming/specification language.  Since the manual construction of tools is expensive, they are hard to obtain and not often used, limiting the quality of the implemented software.  We have proposed a framework for the automated  generation of simulation, analysis and verification tools for programs/specifications based on machine-processable formal definitions of the language's operational semantics.  We also use a modular approach for language semantics that allows us to reuse semantic modules and fragments of already defined tools.

[00_MSc_pinto]
Luís Arthur Ferreira PINTO.  Auditoria gráfica de estruturas de documentos hipermídia no sistema HyperProp. [Title in English: Graphical Auditing of hypermedia document structures in the HyperProp system]. M.Sc. Diss. Port. Presentation: 30/08/2000. 118 p. Advisor: Luiz Fernando Gomes Soares.

Abstract: One of the most important challenges in current hypermedia systems is to provide a graphic interface that helps the visualization of document structure, in order to avoid the common user desorientation.  This thesis proposes a graphical tool for structural navigation and authoring of hypermedia documents based on the Nested Context Model (NCM).  The key features of this tool, a component of the HyperProp System, are the information filtering mechanism and the graph layout techniques, both used to improve the structural view legibility.

[00_PhD_franca]
Luiz Paulo Alves FRANCA.  Um processo para a construção de geradores de artefatos. [Title in English: An artifact generator development process]. Ph.D. Thesis. Port. Presentation: 17/08/2000. 166 p. Advisor: Arndt von Staa.

Abstract: An artifact generator is a software tool which produces an artifact from its high-level specification. An artifact is any item created as part of definition, maintenance or utilization of a software process. Artifact generators are a way to reduce production costs and time to market, and to increase reliability of artifacts within a given application domain. However, in order to achieve a more widespread usage of artifact generators, the difficulty and the cost of their development and maintenance must be reduced. This thesis presents a lowcost artifact generator development and maintenance process. The process departs from an example of a simple artifact within the target application domain. Given this example and considering all possible artifacts of the domain, all commonalties and variabilities are identified, as well as the properties that the specification of each specific target artifact must satisfy. The example is then modified in order to contain specific generator tags at all variable points. These tags establish the transformation rules that must be applied to the specification in order to generate the application. We have used a CASE tool, which allows the programming of the specification editors and of the generators. By means of another tool, the tagged example artifact is transformed into a component, which is combined with the transformation library, yielding the generator code to be internalized by the CASE tool. The process has been successfully used to transform specifications into applications, components and documentation.

[00_MSc_silva]
Marcelo Cabral da SILVA.  Identificação de estilos de arquiteturas: um processo dirigido por conhecimento. [Title in English: Identifying architecture styles: a process driven by knowledge]. M.Sc. Diss. Port. Presentation: 18/09/2000. 194 p. Advisor: Julio Cesar Sampaio do Prado Leite.

Abstract: One of the most recent subjects in the software engineering area, the software architecture, tries to systematize the process of design software, supplying a solid base for the reuse. As more complex systems appear, the importance of system specification and design increases. Therefore software architecture becomes an important discipline. Software architecture is related to the system macro-structure. The architectural vision is an abstract vision of the relationships among the elements comprised by a system, as well as the topology they make up. Algorithm detailment or data representation are not the goals of this thesis. Instead, the composition of the elements that form the architectures and their restrictions will be analyzed. According to our understanding, software architecture is a collection of components, connectors and their behavior restrictions. In other words, software architecture is the collection of the first decisions to be taken during the design phase of a system. In general, these decisions are the most difficult to be taken. After system development, these decisions are the most difficult ones to be modified. Our objective is to provide a method to select architectures based on a requirement list. For such we will count on a knowledge base, as well as on a method. In order to generate the knowledge base, a taxonomy will be defined and based on it relationships among elements will be identified. The collection of relationships among elements will generate architecture styles. In parallel to the architecture style identification study, we will also use concepts of the Requirements Engineering. Therefore, requirements will be used as elements of architecture classification and subsequent selection. A correlation between requirements and elements will be made, starting from each of the identified architectural style.

[00_MSc_antonacci]
Meire Juliana Antonacci.  NCL: uma linguagem declarativa para especificação de documentos hipermídia com sincronização temporal e espacial. [Title in English: NCL: a declarative language for the specification of hypermedia documents with time and space synchronization]. M.Sc. Diss. Port. Presentation: 19/04/2000. 104 p. Advisor: Luiz Fernando Gomes Soares.

Abstract: The main goal of this work is the creation of a declarative language for the specification of hypermedia documents. At first, an analysis of several existing languages is made. Some fundamental characteristics of hypermedia languages are then recognized. Indeed these characteristics derive from hypermedia models the languages are based on. The more expression power models have the more authoring resources they provide allowing the development of complex documents. After analyzing these languages and describing the in models characteristics an analysis and refinement of the NCM hypermedia conceptual model is made with the purpose of providing NCM with all desirable characteristics found in the languages. The creation of a declarative language based on NCM will then provide the same characteristics. The language developed, called NCL, was specified using the XML standard, which defines a markup language recommended by W3C. Through NCL it is possible to specify generic hypermedia documents containing the previously mentioned characteristics, including time and space synchronization relations among their components – this is the main contribution of the present work. Another contribution to be pointed out is the proposal for an extended SMIL, a hypermedia language standardized by W3C, aiming at repairing some SMIL shortcomings and offering the same advantages of NCL.

[00_MSc_sa]
Michele Santos SÁ.  Uma abordagem online para comparação de junções paralelas. [Title in English: An online approach to compare parallel joins]. M.Sc. Diss. Port. Presentation: 15/12/2000. 71 p. Advisor: Sérgio Lifschitz.

Abstract: Different approaches for the parallel execution of the relational join operator were proposed in the literature. Implementations were developed in order to compare and to evaluate these strategies in a parallel environment. However, there is no agreement concerning the behavior of the strategies, with or without load balancing, with respect to several real conditions where these strategies are executed. This work presents an approach to the parallel join problem from the online algorithms theory point of view. We use competitive analysis to evaluate and compare the behavior of strategies compared to the offline (optimal) one. Instead of an analytical study, common to the online context, this dissertation presents an implementation and a simulation to evaluate an online parallel join strategy with load balancing with respect to workload distribution. As adversaries we consider a variation in the number of parallel processors available and the skew on join attribute data values.

[00_PhD_cerqueira]
Renato Fontoura de Gusmão CERQUEIRA.  Um modelo de composição dinâmica entre sistemas de componentes de software. [Title in English: A dynamic composition model among software component systems]. Ph.D. Thesis. Port. Presentation: 21/08/2000. 104 p. Advisor: Noemi da La Rocque Rodriguez and Roberto Ierusalimschy.

Abstract: Different component systems, such as CORBA, COM, and Java, have different object models and type systems. Such differences make the interoperability between components of distinct systems more difficult, and thus are an obstacle for component reuse. In this dissertation, we argue that an interpreted language with a specific set of reflexive mechanisms, together with a type system with structural compatibility, offers a composition mechanism suitable for dynamic component connection and for interoperability between different component systems. This composition mechanism performs at runtime the tasks of verifying types, connecting, adapting and implementing components, and handles components of different systems in a uniform way, allowing them to be connected transparently. The proposed composition mechanism is based on a model that favors flexibility at runtime. This composition model is composed of two major elements. The first one is an object model, defined in order to represent components of the different systems addressed in this dissertation. Thus, this object model performs the role of a unifying model, that is, a model in which objects from different systems can interact and be represented transparently. The second element of our composition model is a design pattern to implement bindings between interpreted languages and component systems. This design pattern, named Dynamic Language Binding, does not use the traditional stubs technique. Instead of this, it uses reflection and dynamic typing to implement generic proxies, which can represent any component of a specific system, and generic adapters, which allow component implementations using the composition language itself. In order to validate our proposal, we describe the LuaOrb system, which is an implementation of our composition model. LuaOrb uses the interpreted language Lua as its dynamic composition language, and integrates the systems CORBA, COM and Java.

[00_MSc_assis]
Rodrigo Lemos de ASSIS.  Facilitando a percepção em ambientes virtuais de aprendizado através da abordadem groupware. [Title in English: Facilitating awareness in virtual learning environments through the groupware approach]. M.Sc. Diss. Port. Presentation: 18/04/2000. 153 p. Advisor: Hugo Fucks.

Abstract: Recent research on groupware and learningware presents some approaches for managing awareness informations in order to enhance cooperation on distributed systems. This work proposes ways to support awareness on learningware environments. The study of awareness in groupware is the first step of this work, which leads to relevant aspects regarding awareness in learningware. Some of these concepts are implemented in the learningware environment AulaNet.

[00_MSc_toledo]
Rodrigo Penteado Ribeiro de TOLEDO.  QuadLOD: uma estrutura para visualização interativa de terrenos. [Title in English: QuaLOD: a struture to interactively visualize terrains]. M.Sc. Diss. Port. Presentation: 11/05/2000. 122 p. Advisor: Marcelo Gattass and Luiz Velho.

Abstract: This work focuses on the use of hierarchical structures to interactively visualize terrain.  Our purpose is to achieve real time three-dimensional visualization of terrain models obtained from a geographic information system.  These models can represent a broad area of the Earth's surface with detailed information, thus yielding very large data sets.  For this reason, it is necessary to use a compatible structure to store and query these data.  In this work, we present a new structure which combines advantages of different structures provided in the literature.  We also discuss an implementation of these ideas and a series of tests, drawing several conclusions.

[00_MSc_torresdasilva]
Viviane Torres da SILVA.  ContentNET: um framework para interoperabiliade de conteúdos educacionais utilizando o padrão IMS. [Title in English: ContentNET: a framework to educational contents interoperability using the IMS platform]. M.Sc. Diss. Port. Presentation: 24/03/2000. 92 p. Advisor: Carlos José Pereira da Lucena.

Abstract: The World Wide Web original organization assumed that its stared information was to be read by machines without concern to the possibility of machines interpreting this information. The growth of the amount of information available on the Web made it more complex to search, have access to and to obtain information on the Web. To cope with this problem the platform IMS has been proposed. A consortium formed by academic institutions, companies and government agencies is developing the platform. The goal of the platform is to promote the viability and growth of online activities in the area of education. One of the most important activities of the consortium in Internet based learning with the possibility of interoperability among different environments for Web-based education. Based on the proposed platform and the need for content exchange among different AulaNet servers we have developed on object oriented framework to enable the description, localization and use of educational content available in servers which are compatible with the IMS platform.

[00_PhD_batista]
Thaís Vasconcelos Batista.  LuaSpace: um ambiente para reconfiguração dinâmica de aplicações baseadas em componentes. [Title in English: LuaSpace: an environment for dynamic reconfiguring component-based application]. Ph.D. Thesis. Port. Presentation: 20/10/2000. 148 p. Advisor: Noemi da La Rocque Rodriguez.

Abstract: Object integration models, also known as component models, present important abstractions to facilitate the development of distributed applications formed by reusable components.  These models offer support to reduce the complexities associated with distributed programming and with the use of heterogeneous components.  In spite of this support, the component models do not provide facilities to describe the global organization of an application. In order to address this issue, we have adopted the configuration-based approach to define the structure of component-based application.  Classically, configuration-based systems follow the Configuration Paradigm, which uses components whose interface describe the services required by clients and those provided by servers.  Therefore, component interactions are described in the configuration program, merely binding required and provided services.  This configuration model is not compatible with components whose interface do not provide information about required services and presents limitations regarding dynamic evolution of application and capacity of adapting components to bridge compositional mismatches.  In ths work, we argue that a different approach, using an interpreted and procedural language as a tool for application configuration, can address this aspect and provide support for an important requirement of nowadays applications: dynamic reconfiguration.  We present an environment, LuaSpace, for configuring and reconfiguring component-based application.  LuaSpace combines the use of heterogeneous and distributed components provided by component models with an interpreted and procedural language, Lua, and a set of tools based on this language.  The environment offers mechanisms for composition and evolution of applications. In this environment, components, scripts and glue code are elements that form an application.  LuaSpace allows adaptation of components that need to bridge compositional mismatches and offers support for programmed, ad-hoc, strucutural and functional reconfiguration and also for dynamic instalation of new components.