Java Language

Gostaria de agradecer a todos os que, de uma forma direta ou indireta, contribuiram para que fosse possível atingir o final desta minha caminhada. Em primeiro lugar não posso deixar de prestar o meu profundo agradecimento ao Professor Pedro Rangel Henriques por toda a dedicação, tempo disponibilizado, persistência e entusiasmo. Sinto-me verdadeiramente previligiada e afortunada por o ter como orientador. Foi um caminho duro mas sem a sua ajuda teria sido seguramente muito mais difícil. Obrigada! À Professora Elsa Gomes, o meu obrigada por todo o suporte e encorajamento, sempre presente e diligente nas suas observações tão pertinentes e oportunas. Foi sem dúvida um pilar importante nesta caminhada estreitando laços de amizade. À Universidade do Minho, em particular ao PDINF, por me ter concedido a oportunidade da realização deste trabalho. Ao ISEP e em particular ao Departamento de Engenharia Informática, pelas facilidades concebidas que possibilitaram a conclusão desta dissertação. Ao Luís Barreiro e Pedro Duarte pelo trabalho efetuado na implementação do PEP. À Bertil e ao Marílio o meu obrigada pela amizade demonstrada ao longo destes anos e pela paciência e apoio incondicional. À Rosa Reis pela ajuda dada, principalmente na difícil fase final. Aos colegas com quem trabalho, em particular os das unidades curriculares que leciono, por todo o apoio e compreensão ao longo deste percurso. Ao Miguel, pelo grande "empurrão" que me permitiu chegar até aqui! VIII Às pessoas cujo convívio é muito anterior ao início desta caminhada e que foram importantes para aqui chegar. Em particular à minha família, porto de abrigo, nos bons, mas principalmente nos momentos mais difíceis, por todo apoio, compreensão e incentivo. Ao meu pai e à minha mãe pelo apoio total e incondicional. Sem a sua ajuda de certeza que tudo seria mais difícil. Obrigada! Foi o seu exemplo inspirador que me permitiu aqui chegar. Sem eles não teria conseguido. À João, um exemplo de força, pelas palavras encorajadoras! Sempre. Obrigad Fernando. Mesmo com o seu silêncio, o seu exemplo de persistência permitiu-me perceber que somos sempre capazes. O caminho foi duro e longo mas a compreensão esteve sempre presente. À Rita, pelas muitas horas que lhe "roubei" e pela sua compreensão. Que este seja um esforço inspirador para a sua realização pessoal e profissional. X Por fim ainda se estudou a importância de incluir no sistema de apoio ao ensino elementos dos jogos que estimulam a motivação e ainda se propôs um enriquecimento do sistema PEP através da inclusão de técnicas de ludificação ou gamificação.

Traditionally, parallel programs have been developed in Fortran and C. However, the extraordinary success of the Java language has raised an impressive hype among the community of software programmers, in such a way that it seems quite promising that parallel programmers could also use Java in their applications. In this paper, we describe the implementation of Java interface for WMPI, a Windows-based implementations of MPI that have been developed and supported by our group. We show some details about the implementation and we present some experimental results that compare the performance of Java WMPI, Java WPVM and the C programs counterparts.

Grid portals provide the scientific community with familiar and simplified interfaces to the Grid and Grid services, and it is important to deploy grid portals onto the SciDAC grids and collaboratories. The goal of this project is the research, development and deployment of interoperable portal and web services that can be used on SciDAC National Collaboratory grids. This project has four primary task areas: development of portal systems; management of data collections; DOE science application integration; and development of web and grid services in support of the above activities. The Portal Web Services project team is funded to develop and deploy interoperable portal and Grid/Web services that can be used in support of numerous SciDAC Grid projects. Our efforts concentrate on four primary tasks: the development of portal systems, management of data collections, migration of technologies from the DOE sponsored CCA project, and the development of Web services in support of the above activities. Initial deployment will be on the Fusion Grid project, although developed technologies will be of general usefulness to other SciDAC/DOE Grid efforts. As we describe in "Synergistic Activities", we are well positioned to contribute to other SciDAC efforts such as CMCS. The focus in this first year has been on the investigation of emerging grid and portal technologies and starting up the project. • Project website launched: • Open Grid Computing Environments Consortium (OGCE) formed • Portlets developed for Grid information browsing, MyProxy login, GridFTP access, and basic Grid job launching capabilities. • GPIR Web services up and running on TeraGrid. • SDSC releases version 2.0 of the Storage Resource Broker • FusionGrid portal architecture conceptualized • Fusion codes G2/TRANSP running on FusionGrid.

This study proposes a multi-pass compiler with code optimized abstract syntax tree based on a subset of C# as the source and C constructs as the target, with the view to enhancing the understanding of compiler design, which conceptually has been a rather difficult discourse. A single-pass compiler allows a single traversal over the source code or intermediate form. This does not allow for a distributed compilation and modular development. On the other hand, the proposed scheme decouples the type-checker from the abstract syntax tree, thus separating them into independent segments that allows a multi-pass over the source code; this in turn provides a mechanism for modular development, which encourages distributed compilation. The proposed scheme constructs the abstract syntax tree before the typechecking, thus allowing another tranversal on the intermediate form of the source code. An optimised tree was constructed after code optimisation had been conducted. The scheme is based on only small subset of C# constructs. Further study would be focused on adding more constructs.

We propose a method which allows us to develop tableaux modulo theories using the principles of superdeduction, among which the theory is used to enrich the deduction system with new deduction rules. This method is presented in the framework of the Zenon automated theorem prover, and is applied to the set theory of the B method. This allows us to provide another prover to Atelier B, which can be used to verify B proof rules in particular. We also propose some benchmarks, in which this prover is able to automatically verify a part of the rules coming from the database maintained by Siemens IC-MOL.

We propose a formal and mechanized framework which consists in verifying proof rules of the B method, which cannot be automatically proved by the elementary prover of Atelier B and using an external automated theorem prover called Zenon. This framework contains in particular a set of tools, named BCARe and developed by Siemens IC-MOL, which relies on a deep embedding of the B theory within the logic of the Coq proof assistant. This toolkit allows us to automatically generate the required properties to be checked for a given proof rule. Currently, this tool chain is able to automatically verify a part of the derived rules of the B-Book, as well as some added rules coming from Atelier B and the rule database maintained by Siemens IC-MOL.

Data mining deals with the discovery of hidden knowledge, unexpected patterns and new rules from large database, Basically it is concerned with the analysis of data and the use of software techniques for finding patterns in sets of data, one of its main terms is the clustering, which is mean, the process of dividing a database into mutually exclusive groups such that the members of each group are as close as possible to one another , and different groups are as far as possible from one another , where distance is measured with respect to all available variables.
            Clustering is perhaps the most frequently used data mining algorithm, being useful in its own right as an exploratory technique, and also as a subroutine in more complex data mining algorithms such as rule discovery, indexing, summarization, anomaly detection, and classification, In the last decade the educational institutions began to apply the standards of quality and accreditation, one of the most important standards is the( Planning and Evaluation) therefore; all the educational institutions activities must be evaluate according to logical and scientific methods,      clustering methods have been applied in this research for a real cases concerned with Foundation Technical Institutes (FTE) to have fairly evaluation of performance among FTE branches in giving educational courses to the society(year 2006-2009 ),Complete Linkage method gives perfect and meaningful structure to have analytical method  for fairly evaluation of performance to be identical with the standards of quality and accreditation, while the traditional evaluation depends only on the number of courses.

Canica is an integrated development environment for the Java Modeling Language (JML), a formal behavioral interface specification language for Java. The JML distribution includes several support tools, such as a syntax checker, a compiler, and a document generator, and there are several third-party tools available for JML. However, most of these tools are command-line-based and work in isolation. Canica glues and streamlines these tools to provide a GUI-based, integrated environment for JML; for example, it automates unit testing including test data generation, test execution, and test result determination. In this paper, we describe the key features of Canica and explain its design and implementation. We also discuss the lessons that we learned from our development effort.

This paper presents Java language from an object-oriented software construction perspective. It explains the implications of banning generics and multiple inheritance of classes, and explores the patterns and the idioms used by the Java designers and programmers to redeem their beneÿts. The paper also discusses an alternative to multiple inheritance, as incorporated in Lava, which extends Java with constructs for type-safe automatic forwarding.

Code coverage information is widely used to address problems in software development and maintenance phase. Software undergoes changes at all stages of the software development process and in maintenance life cycle. As subsequent versions of software program are created, coverage data is needed for those programs for regression testing tasks. Code coverage information helps in selecting test cases that are

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Decompiling is often used in conjunction with recovering lost source code, or in reverse-engineering code when we do not have access to the source. Here we describe a novel use: places where accurate position reporting, even in the presence of optimized code or where source code is not available, could be helpful. Examples include tracebacks, debuggers, core dumps and so on. Also new is using decompilation to assist debugging at runtime. We show how more conventional methods of source-code reporting are vague and ambiguous. Although effecting a pervasive change in a compiler is arduous and error-prone, a decompiler can be developed somewhat independently. However, for the vast number of programming languages, decompilers do not exist. This is true even for dynamic interpreted languages where there is little going on in the way of “compilation.” Traditionally, decompilers are labor intensive and ad hoc, and their construction might also be unfamiliar. So this paper shows how to ameli...

GPSS has been used for years to teach simulation. Different tools following the GPSS syntax exist. Usually these tools can be used to construct simulation models helping in the teaching of simulation. However no available framework is capable to simplify the development of a complete simulation tool following the GPSS syntax. This paper presents JGPSS, a framework based in Java language that can be used by students to build a complete simulation tool following the GPSS syntax. JGPSS has two versions, one capable to perform simulations and obtain statistical information, and other designed as a framework for students of computer sciences. This last framework, described in this paper, lacks in the implementation of the main simulation engine algorithms or the related structures. This framework allows the computer science student to reach a deeper understanding of how to construct a complete process interaction simulation engine, the paradigm that GPSS follows.

Dynamic networks-spontaneous, self-organizing groups of devices-are a promising new computing platform. Writing applications for such networks is a daunting task, however, due to their extreme variability and unpredictability, with many devices having significant resource limitations. Intelligent, automated distribution of work across network nodes is needed to get the most out of limited resource budgets. We propose a novel framework for distributing computations across a dynamic network, in which applications specify their spatiotemporal properties at a very high level. The underlying system makes node selection decisions to exploit these properties, producing high quality results within a fixed resource budget. A distributed computation is expressed as a semantically parallel loop over a geographic area and time period. Feedback from the application about the quality of node selection decisions is used to guide future decisions, even while the loop is still in progress. This simplifies the process of writing dynamic network applications by allowing programmers to focus on the goals of their applications, rather than on the topology and environment of the network. Our framework implementation consists of extensions to the Java language, a compiler for this extended language, and a run-time system that work together to provide a simple, powerful architecture for dynamic network programming. We evaluate our system using 11 Nokia N810 tablet PC devices and 14 Neo FreeRunner (Openmoko) smartphones, as well as a simulation environment that models the behavior of up to 500 devices. For three representative applications, we obtain significant improvements in the number of useful results obtained when compared with baseline node selection algorithms: up to 745% (measured), 117% (simulated) for an Amber Alert application; 38% (measured), 142% (simulated) for a Bird Tracking application; and 86% (measured), 209% (simulated) for a Crowd Estimation application.

La ciudad de Guayaquil, Ecuador, es conocida sobre todo por su aspecto comercial, por encima del turístico. De hecho, arquitectónicamente hablando y salvo ciertas estructuras, la ciudad no destaca por poseer un centro histórico reconocido, tal como otras urbes del mismo país o Latinoamérica (Santana, 2015).

The power of languages is rooted in composition. An infinite number of sentences can be composed from a finite set of generative rules. The more uniformly the rules apply, the more valid compositions there are. Hence simpler rules give rise to richer discourse-a case of 'less is more'. We must however be careful as to which distinctions we preserve and which we eliminate. If we abstract too much we risk creating an undifferentiated soup with no landmarks to orient us. A uniform space of objects with simple rules governing their interaction is an obvious example of these ideas, but objects also serve as a cautionary tale. Achieving simplicity is not easy; it requires taste, judgement, experience and dedication. Ingenuity is essential as well, but left unchecked, it often leads to uncontrollable complexity. The path of least resistance follows the tautological principle that 'more is more', and who can argue with a tautology? Dissonance dominates. I will endeavour to i...

We present GJ, a design that extends the Java programming language with generic types and methods. These are both explained and implemented by translation into the unextended language. The translation closely mimics the way generics are emulated by programmers: it erases all type parameters, maps type variables to their bounds, and inserts casts where needed. Some subtleties of the translation are caused by the handling of overriding.GJ increases expressiveness and safety: code utilizing generic libraries is no longer buried under a plethora of casts, and the corresponding casts inserted by the translation are guaranteed to not fail.GJ is designed to be fully backwards compatible with the current Java language, which simplifies the transition from non-generic to generic programming. In particular, one can retrofit existing library classes with generic interfaces without changing their code.An implementation of GJ has been written in GJ, and is freely available on the web.

We describe the use and implementation of mixins in the Animorphic Smalltalk system, a high performance Smalltalk virtual machine and programming environment. Mixins are the basic unit of implementation, and are directly supported by the VM. At the language level, code can be defined either in mixins or in classes, but classes are merely sugar for mixin definition and application. The Strongtalk type system supports the optional static typechecking of mixins in an encapsulated manner. Independent of typechecking, the resulting system system substantially outperforms existing Smalltalk implementations.

A novel approach to the runtime visualization and analysis of object-oriented programs is presented and illustrated through a prototype system called JIVE: J ava I nteractive V isualization E nvironment. The main contributions of JIVE are: multiple concurrent representations of program state and execution history; support for forward and reverse execution; and graphical queries over program execution. This model facilitates program understanding and interactive debugging. Our visualization of runtime states clarifies the important point that objects are environments of execution. The history of object interaction is displayed via sequence diagrams, and in this way we help close the loop between design-time and run-time representations. Interactive execution is made possible by maintaining a runtime history database, which may be queried for information on variable behavior, method executions, and object interactions. We illustrate the capabilities of this system through examples. JIVE is implemented using the Java Platform Debugger Architecture and supports the Java language and libraries, including multithreaded and GUI applications.

The subject of my Master Thesis in Computer Science has been to write a compiler which implements the OpenMP specification for C, and generates C code using POSIX threads (a.k.a. pthreads) to implement the parallelism. I first approached the problems by attempting to develop a mechanical way to manually translate an OpenMP program into an equivalent program using pthreads. In this process, I had to solve a number of conceptual problems – pthreads offer a granularity of parallelism at the level of one function, which is quite radically different from what OpenMP offers. Likewise, I had to investigate, understand and solve such problems as thread initialization, how to implement threadprivate variables, or how to handle the fact that source code can come in more than one file. Also, while the main focus was to investigate the viability of doing this at all, I could not entirely lose sight of performance issues, both regarding memory use and overhead introduced into the code by the tra...

We describe an extension to the Java language, Handi-Wrap, that supports weaving aspects into code at runtime. Aspects in Handi-Wrap take the form of method wrappers, which allow aspect code to be inserted around method bodies like advice in AspectJ. Handi-Wrap offers several advantages over static aspect languages such as AspectJ. First, aspects can be woven into binary libraries. Second, a wrapper in Handi-Wrap is a first-class Java value, which allows users to exploit Java mechanisms to define and weave wrappers. For example, wrappers can be passed explicit constructor arguments, and wrapper objects can be composed. Finally, methods in all Java classes, including anonymous classes, can be wrapped. A prototype of Handi-Wrap is implemented in a compile-time metaprogramming system for Java, called Maya; we briefly describe how Maya's features support Handi-Wrap.

Teaching a new programming language in CS1 requires the instructor to make several important decisions regarding sequencing of topics. In teaching Java, the basic decisions center around how to perform input and output, when to teach the AWT ( Window Toolkit) and threads, whether to begin with applets or applications, and how much detail about object-oriented programming and Java language features is required in the beginning. This paper describes a "language features gently" approach to teaching CS1 in Java.

We propose a Globally Asynchronous Locally Synchronous language DSystemJ for designing dynamic distributed systems. DSystemJ, an extension of the reactive asynchronous SystemJ language, enhances it with dynamic creation and process mobility, and uses the Java language for programming sequential data computations. Moreover, DSystemJ is equipped with a formal semantics, which allows, formal system specification, reasoning, and automatic code generation. Compared to special purpose languages, DSystemJ is better in terms of implementation, scalability, and features. Compared to general purpose languages, DSystemJ is better because it exposes, at the language level, OS features like communication, concurrency, process creation and migration, therefore making it better suited for system level design of complex distributed systems.

The lack of direct support for multidimensional arrays in Java TM has been recognized as a major deficiency in the language's applicability to numerical computing. The typical approach to adding multidimensional arrays to Java has been through class libraries that implement these structures. It has been shown that the class library approach can achieve very high-performance for numerical computing, through the use of compiler techniques and efficient implementations of aggregate array operations. Because of the inconvenience of accessing array elements through method invocations, it is advocated by many that class libraries for multidimensional arrays should be combined with new language syntax to facilitate manipulation of those multidimensional arrays. Another approach that has been discussed in the literature is that of relying exclusively on the JVM to recognize those arrays of arrays that are being used to simulate multidimensional arrays. This approach can also deliver good performance, but it does not improve the existing interfaces for numerical computing. There is yet a third approach: extending the Java language with new syntactic constructs for multidimensional arrays and directly compiling those constructs to bytecode. The new constructs provide a more convenient interface for numerical computing, without requiring a matching class library. This paper is a comparative discussion of the three approaches to adding multidimensional arrays to Java mentioned above. We present a description of the three approaches, listing the pros and cons of each. We give a more detailed description of the third approach-language constructs translated to bytecode-as it is a new contribution. We compare each of the approaches with regards to functionality, impact on the language and virtual machine specification, implementation efforts, and typical achievable performance. We show that the best choice depends on the relative importance attached to the above metrics.

One glaring weakness of Java for numerical programming is its lack of support for complex numbers. Simply creating a Complex number class leads to poor performance relative to Fortran. We show in this paper, however, that the combination of stich a Complex class and a compiler that understands its semantics does indeed lead to Fortran-like performance. This performance gain is achieved while leaving the Java language completely unchanged and maintaining full compatibility with existing Java Virtual Machines. We quantify the effectiveness of our approach through experiments with linear algebra, electromagnetics, and computational fluid-dynamics kernels.

This paper presents an object oriented framework for task scheduling. This framework can be used in domains such as Process-centred Software Engineering Environments, Workflow Management Systems or Project Management Systems. The framework was conceived based on both current methods for the development of frameworks and an existing architectural pattern for process managers. A prototype of the framework was developed using the Java Language. The lessons learnt show the experience of extracting a framework from well-known applications that can be reused in practical domains. Thus, this work contributes not only in the production of a framework but also giving insights in the application of novel techniques to the development of frameworks.

MPJ Express is a thread-safe Java messaging library that provides a full implementation of the mpiJava 1.2 API specification. This specification defines a MPI-like bindings for the Java language. We have implemented two communication devices as part of our library, the first, called niodev is based on the Java New I/O package and the second, called mxdev is based on the Myrinet eXpress library. MPJ Express comes with an experimental runtime, which allows portable bootstrapping of Java Virtual Machines across a cluster or network of computers. In this paper we describe the implementation of MPJ Express. Also, we present a performance comparison against various other C and Java messaging systems. A beta version of MPJ Express was released in September 2005.

Successful programming languages change as they age. They tend to become more complex, and eventually some features become outdated or are rarely used. Programming tools for these languages become more complex as well, since they have to support archaic features. Old programs are hard to maintain, since these archaic features are unfamiliar to modern programmers. These problems can be solved by refactoring tools that can transform programs to use the modern form. We show that refactoring tools can ease the cost of program evolution by examining the evolution of two languages, Fortran and Java, and showing that each change corresponds to an automatable refactoring.

-Muitos alunos apresentam dificuldades na compreensão e desenvolvimento de algoritmos. Para tentar ajudar esses alunos foi criado o ambiente SICAS, um ambiente de trabalho individual baseado na animação e simulação de algoritmos. Neste artigo iremos apresentar o SICAS-COL, um sistema colaborativo destinado ao auxílio da aprendizagem da programação. O SICAS-COL é uma evolução deste ambiente que procura aliar a animação e simulação de algoritmos com actividades colaborativas de aprendizagem. Estas permitem que um grupo de alunos colabore na resolução de um problema através de actividades de desenvolvimento, comentário e argumentação por todos os elementos do grupo. Palavras Chave -aprendizagem da programação, animação de algoritmos, CSCL.

Key management comprises a set of methods to support aspects related to keys in cryptographic purposes. Important features related to key management are: generation, distribution, backup, and storage of the keys involved in secure communication. Key management is an essential part of cryptography due to the fact that message secrecy and all the secure communication are compromised if some information about the key is revealed . Key management in publickey cryptography is easier than in symmetrickey systems. In order to encrypt data, only public key is required. Authentication of the public key user is necessary, but not the key secrecy. Key exchange for symmetrickey systems can be performed in different ways as described below. Adleman began the new field of bio-molecular computing research. His idea was to use DNA biochemistry for solving problems that are impossible to solve by 680-099 12

In this paper we review the essence of the Grid-Idea. Specifically, we explore the changing definition of the Grid and follow its evolution over the past decade. This evolution is motivated by the gradual expansion of management issues that must be addressed to make production Grids a reality and to meet user requirements for increased functionality. Additionally, we focus on the evolutionary path of the Globus Toolkit taken to address the increasing needs of the community. We also discuss the evolutionary inclusion of commodity technologies as illustrated by the Java Commodity Grid Project.

Many scientific simulations and experiments require the coordination of numerous tasks posed by interdisciplinary research teams. Grids can provide access to the necessary high-end resources to conduct such tasks. The complex tasks and their interactions must be supported through convenient tools. To address this issue, we introduce a number of Grid abstractions that make the development of Grid middleware-independent tools possible and allow for the integration of a number of commodity tools. Our vision is implemented through an integrated approach based on a layered architecture that bridges the gap between Grid middleware and scientific applications. Our abstractions include specialized services, a Grid workflow engine and language, and Grid faces -graphical abstractions that can be employed in science portals and standalone applications.

A~tract-The current development of the World Wide Web (W3), the globally interlinked hypermedia network of text, pictures and images, presents unique opportunities for education. The distributed nature of the W3, and the ease with which users can gain access and contribute to it sets it apart from any other hypermedia system. However, to date the W3 has been used predominantly as a means of delivering information, either in the form of lecture notes or virtual libraries. Such usage neglects the power of the W3 as an environment through which programs may be accessed and controlled interactively. The capabilities of the W3 in the latter respect are e~olving at an enormous rate. If education is to exploit the tools so provided, it must cease to view the W3 as a simple authoring environment and instead consider how the access to applications that this environment can provide can be harnessed in support of the learning process itself and in the management of the educational environment of the student. The above argument is illustrated by examples taken from the Interact project, which was the first TLTP (Teaching and Learning Technology Programme) project to utilize W3 technology. Within this project two tools were developed, the Interact Communication Facility (ICF) and the Presentation Manager (PM). The ICF permits simulations to be integrated into the hypermedia environment provided by W3 while the PM provides greater and more convenient control over simulations so integrated. These tools permitted the creation of a learning environment, the Interact Simulation Environment (ISE), which greatly extends the availability of the simulations as a learning resource and the opportunity for dialogue about the simulations as they are used in learning. The basic principles which underpin the creation of this environment in engineering are shown to be extensible to other domains and to non-Interact based applications. In a separate but related project, commercial applications such as MATLAB are also shown to be controllable over the W3. The weaknesses of the 1SE are, however, also discussed and the benefits liable to be accrued from re-implementation of this environment in Sun's new Java language are considered. The potential of Sun's new browser Hotjava to further revolutionalize the educational opportunities provided by the W3 is seen to be but further evidence of the dynamic nature and real opportunity that this new technology provides for education.

Due to the successful development of the Internet, the course of distributed systems has received great attention by many universities and colleges in their computer science curricula. A comprehensive distributed system course involves many disciplines, such as ...

This article describes the transposition of cartographic concepts to virtual reality (VR) applications. Versions of cartographic maps can be created by using Generalization. These versions can be implemented for VR applications using Levels of Detail. Cartographic Generalization is concerned with model visualization that uses twelve operators and domain-specific knowledge. There is no known transposition of these operators and knowledge to the VR realm. We present an analysis of these operators in the context of VR. A system for 3D Generalization is proposed. Artificial intelligence techniques are used for both selecting the key objects and applying the operators. This system was implemented with the JAVA language, modelled with UML and employs a MySQL database.

This paper describes Janet package-highly expressive Java language extension that enables convenient creation of powerful native methods and efficient Java-to-native code interfaces. Java native interface (JNI) is a low-level API that is rather inconvenient if used directly. Therefore Janet, as the higher-level tool, combines flexibility of JNI with Java's ease-of-use. Performance results of Janet-generated interface to the lip library are shown. Java code, which uses lip, is compared with native C implementation.

Java is growing in appropriateness and usability for high performance computing. With this increasing adoption, issues relating to combining Java with existing codes in other languages become more important. The Java Native Interface (JNI) API is portable but too inconvenient to be used directly owing to its low-level API. This paper presents Janet-a highly expressive Java language extension and preprocessing tool that enables convenient integration of native code with Java programs. The Janet methodology overcomes some of the limitations of JNI and generates Java programs that execute with little or no degradation despite the flexibility and generality of the interface.

This paper describes Janet package-highly expressive Java language extension that enables convenient creation of powerful native methods and efficient Java-to-native code interfaces. Java native interface (JNI) is a low-level API that is rather inconvenient if used directly. Therefore Janet, as the higher-level tool, combines flexibility of JNI with Java's ease-of-use. Performance results of Janet-generated interface to the lip library are shown. Java code, which uses lip, is compared with native C implementation.

The main goal of the research proposed in this document is to reduce the cost of developing and maintaining large software applications. Our approach augments existing object-oriented languages with a small number of domain-independent features designed to enhance code reusability, thus making applications easier to build. This proposal describes the contributions we expect our research to make.

In object-oriented languages, aspects can be defined by generalizing the idea of a class to that of a mixin. Mixins, which can be implemented as generic types, become aspects when they contain code for multiple classes. In this chapter, we describe mixins and we explain how mixins can be used to define aspects. We demonstrate the flexibility of mixin programming by prototyping a graphical user interface library that can be configured to run on dissimilar devices. We describe additional language and compiler sup-2 Chapter 33 Using Mixin Technology to Improve Modularity port that increases the effectiveness of mixin programming. We conclude by proposing some new ideas about how mixins, and generic types in general, can be better supported in object-oriented languages. 33.1. INTRODUCTION One approach to reducing the cost of software is to make software easier to reuse and, in doing so, to reduce the risk and expense of developing new applications. If existing software can be reused, then the cost of developing and maintaining new code can be significantly reduced. This ability to reuse code depends on two properties: modularity and easy composition. Modularity allows us to separate concerns [26], making code easier to understand, maintain, and treat as a unit. Easy composition allows us to combine the capabilities of different code modules in different applications. Unfortunately, today's object-oriented languages, such as Java, are limited in their ability to modularize and compose code. Modularity is limited because the basic unit of encapsulation and reuse is the class. Once the organization of a class hierarchy is fixed, it is always possible to define new

In this paper we present StarFish, a highly-available geographically-dispersed block storage system built from commodity servers running FreeBSD, which are connected by standard high-speed IP networking gear. StarFish achieves high availability by transparently replicating data over multiple storage sites. StarFish is accessed via a host-site appliance that masquerades as a host-attached storage device, hence it requires no special hardware or software in the host computer. We show that a StarFish system with 3 replicas and a write quorum size of 2 is a good choice, based on a formal analysis of data availability and reliability: 3 replicas with individual availability of 99%, a write quorum of 2, and read-only consistency gives better than 99.9999% data availability. Although StarFish increases the per-request latency relative to a direct-attached RAID, we show how to design a highly-available StarFish configuration that provides most of the performance of a direct-attached RAID on...

Este trabalho apresenta a descrição do projeto de um conjunto de ferramentas que se aplica às tarefas de gerenciamento de materiais didáticos apresentados no ambiente WWW. A proposta deste trabalho está centrada no desenvolvimento de mecanismos para a interação entre as entidades aluno e professor com o curso disponibilizado através do ambiente WWW, utilizando-se da tecnologia de agentes de software. O uso do conceito de agentes de software neste trabalho é justificado pela necessidade de isolamento dos professores e alunos das tarefas computacionais do gerenciamento. Em adição, é importante ressaltar que o desenvolvimento das ferramentas envolve a utilização da linguagem JAVA, o que reforça a facilidade de intercâmbio de informações com outras aplicações, por exemplo com ferramentas de autoria de materiais didáticos em ambientes multiplataforma.

En las ciudades de América Latina las desigualdades urbanas se sostienen por el sistema económico, el Estado y la sociedad civil. Si comprendemos el urbanismo como el diseño, la construcción, el uso y la gestión del espacio urbano, es posible analizar cómo se centra la atención en las necesidades de unos cuerpos y movilidades en específico y no de toda la población que las utiliza o necesita emplearlas al habitar la ciudad; se expresa, entonces, el urbanismo capacitista. El objetivo de este artículo es presentar algunos hilos de un tejido para analizar las redes de desigualdades urbanas elaborado desde el acercamiento a las movilidades de las personas con discapacidad con el interés de conocer cómo se corporeizan dichos fenómenos sociales. El artículo presenta, a través de la exploración corporal, la experiencia de las personas con discapacidad en ciudades que arrinconan en Costa Rica.

In this paper we present some experiences with the use of the conjugate gradient and GMRES iterative methods for the solution of large sparse systems of equations as recently implemented in ADINA and ADINA-F for structural and fluid flow problems. The conjugate gradient method preconditioned with the incomplete Cholesky decomposition is used for the symmetric positive definite systems resulting from structural problems. For fluid flow problems, the systems of equations are nonsymmetric and indefinite. For these systems, the biconjugate gradient and GMRES algorithms with preconditioning by incomplete LU factorization are used. The performance of the iterative methods is compared with the direct solution methods. The results from our numerical experiments show that the use of these iterative methods for large sparse systems can lead to significant reductions in storage requirements and computation times, especially for nonlinear structural dynamics problems and threedimensional problems in general.