Data Persistence in Eiffel

This dissertation describes an extension to the Eiffel programming language that provides automatic object persistence (the ability of programs to store objects and later recreate those objects in a subsequent execution of a program). The mechanism is orthogonal to other aspects of the Eiffel language. The mechanism serves four main purposes: 1) it gives Eiffel programmers a needed service, filling a gap between serialization, which provides limited persistence functions and database-mapping, which is cumbersome to use; 2) it greatly reduces the coding burden incurred by the programmer when objects must persist, allowing the programmer to focus instead on the business model; 3) it provides a platform for testing the benefits of orthogonal persistence in Eiffel, and 4) it furnishes a model for orthogonal persistence in other object-oriented languages. During my research, I created a prototype implementation of the persistence mechanism using it effectively in several programs. Performance measurements showed acceptable performance with some increase in program memory usage. The prototype gives the programmer the ability to add automatic persistence to existing code with the addition of only a few lines of code. The size of this additional code remains constant regardless of the total number of lines of code in the project. Eiffel syntax remains unchanged and nonpersistent Eiffel code runs as is while incur- ring only a very small speed penalty

An Ada-like language to facilitate reliable coding of low cost embedded systems

Due to a lack of operating system (0/S) support, it is more difficult to develop programs for embedded systems than for workstations. For those developing on a low budget, the problem is often further compounded by the necessity of using inappropriate, 0/S dependent, compilers. This study attempts to ascertain those elements of a High Level Language (HLL) which are absolutely necessary and implementable to produce reliable, efficient, embedded programs without the benefit of a large budget. The study is based upon the Ada philosophy as the Ada language incorporates many desirable features for modelling real-world problems in terms of embedded solutions. By implication, the research provides a small step towards an increased availability of low cost tools to assist in the development of reliable and efficient code for use in medium performance embedded systems

Critters in the Classroom: A 3D Computer-Game-Like Tool for Teaching Programming to Computer Animation Students

The brewing crisis threatening computer science education is a well documented fact. To counter this and to increase enrolment and retention in computer science related degrees, it has been suggested to make programming "more fun" and to offer "multidisciplinary and cross-disciplinary programs" [Carter 2006]. The Computer Visualisation and Animation undergraduate degree at the National Centre for Computer Animation (Bournemouth University) is such a programme. Computer programming forms an integral part of the curriculum of this technical arts degree, and as educators we constantly face the challenge of having to encourage our students to engage with the subject. We intend to address this with our C-Sheep system, a reimagination of the "Karel the Robot" teaching tool [Pattis 1981], using modern 3D computer game graphics that today's students are familiar with. This provides a game-like setting for writing computer programs, using a task-specific set of instructions which allow users to take control of virtual entities acting within a micro world, effectively providing a graphical representation of the algorithms used. Whereas two decades ago, students would be intrigued by a 2D top-down representation of the micro world, the lack of the visual gimmickry found in modern computer games for representing the virtual world now makes it extremely difficult to maintain the interest of students from today's "Plug&Play generation". It is therefore especially important to aim for a 3D game-like representation which is "attractive and highly motivating to today's generation of media-conscious students" [Moskal et al. 2004]. Our system uses a modern, platform independent games engine, capable of presenting a visually rich virtual environment using a state of the art rendering engine of a type usually found in entertainment systems. Our aim is to entice students to spend more time programming, by providing them with an enjoyable experience. This paper provides a discussion of the 3D computer game technology employed in our system and presents examples of how this can be exploited to provide engaging exercises to create a rewarding learning experience for our students

Processes in KaffeOS: lsolation, resource management, and sharing in Java

Journal ArticleSingle-language runtime systems, in the form of Java virtual machines, are widely deployed platforms for executing untrusted mobile code. These runtimes provide some of the features that operating systems provide: inter-application memory protection and basic system services. They do not. however, provide the ability to isolate applications from each other, or limit their resource consumption. This paper describes KaffeOS, a system that provides these features for a Java runtime. The KaffeOS architecture take many lessons from operating from operating system design, such as the use of a user/kernel boundary

Supporting the evolution of software

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A software restructuring tool for oberon

Thesis (MComm) -- University of Stellenbosch, 2001.ENGLISH ABSTRACT: Software restructuring is a form of perfective maintenance that modifies the structure of a program's source code. lts goal is increased maintainability to better facilitate other maintenance activities, such as adding new functionality or correcting previously undetected errors. The modification of structure is achieved by applying transformations to the source code of a software system. Software engineers often attempt to restructure software by manually transforming the source code. This approach may lead to undesirable and undetectable changes in its behaviour. Ensuring that manual transformations preserve functionality during restructuring is difficult; guaranteeing it is almost impossible. One solution to the problem of manual restructuring is automation through use of a restructuring tool. The tool becomes responsible to examine each transformation and determine its impact on the software's behaviour. If a transformation preserves functionality, it may be applied to produce new source code. The tool only automates the application of transformations. The decision regarding which transformation to apply in a specific situation still resides with the maintainer. This thesis describes the design and implementation of a restructuring tool for the Oberon language, a successor of Pascal and Modula-2, under the PC Native Oberon operating system. The process of creating an adequate abstraction of a program's structure and its use to apply transformations and generate new source code are investigated. Transformations can be divided into different classes: Scoping, Syntactic, Control flow and Abstraction transformations. The restructuring tool described in this thesis contains implementations from all four classes. Informal arguments regarding the correctness of each transformation are also presented.AFRIKAANSE OPSOMMING: Die herstrukturering van programmatuur is daarop gemik om die struktuur van 'n program se bronkode te wysig. Hierdie strukturele veranderings dien in die algemeen as voorbereiding vir meer omvangryke onderhoudsaktiwiteite, soos byvoorbeeld die toevoeging van nuwe funksionaliteit of die korrigering van foute wat voorheen verskuil was. Die verandering in struktuur word teweeggebring deur die toepassing van transformasies op die bronkode. Programmatuur-ontwikkelaars voer dikwels sulke transformasies met die hand uit. Sulke optrede kan problematies wees indien 'n transformasie die funksionaliteit, in terme van programgedrag, van die programmatuur beïnvloed. Dit is moeilik om te verseker dat bogenoemde metode funksionaliteit sal behou; om dit te waarborg is so te sê onmoontlik. 'n Oplossing vir bogenoemde probleem is die outomatisering van die herstruktureringsproses deur die gebruik van gespesialiseerde programmatuur. Hierdie programmatuur is in staat om die nodige transformasies toe te pas en terselfdertyd funksionaliteit te waarborg. Die keuse vir die toepassing van 'n spesifieke transformasie lê egter steeds by die programmeerder. Hierdie tesis bespreek die ontwerp en implementering van programmatuur om bronkode, geskryf in Oberon (die opvolger van Pascal en Modula-2), te herstruktureer. Die skep van 'n voldoende abstrakte voorstelling van bronkode, die gebruik van sodanige voorstelling in die toepassing van transformasies en die reprodusering van nuwe bronkode, word bespreek. Transformasies kan in vier breë klasse verdeel word: Bestek, Sintaks, Kontrolevloei en Abstraksie. Die programmatuur wat ontwikkel is vir hierdie tesis bevat voorbeelde uit elkeen van die voorafgenoemde klasse. Informele argumente word aangebied om die korrektheid van die onderskeie transformasies te staaf

LF : a language for reliable embedded systems

Thesis (MSc)--University of Stellenbosch, 2001.ENGLISH ABSTRACT: Computer-aided verification techniques, such as model checking, are often considered essential to produce highly reliable software systems. Modern model checkers generally require models to be written in eSP-like notations. Unfortunately, such systems are usually implemented using conventional imperative programming languages. Translating the one paradigm into the other is a difficult and error prone process. If one were to program in a process-oriented language from the outset, the chasm between implementation and model could be bridged more readily. This would lead to more accurate models and ultimately more reliable software. This thesis covers the definition of a process-oriented language targeted specifically towards embedded systems and the implementation of a suitable compiler and run-time system. The language, LF, is for the most part an extension of the language Joyce, which was defined by Brinch Hansen. Both LF and Joyce have features which I believe make them easier to use than other esp based languages such as occam. An example of this is a selective communication primitive which allows for both input and output guards which is not supported in occam. The efficiency of the implementation is important. The language was therefore designed to be expressive, but constructs which are expensive to implement were avoided. Security, however, was the overriding consideration in the design of the language and runtime system. The compiler produces native code. Most other esp derived languages are either interpreted or execute as tasks on host operating systems. Arguably this is because most implementations of esp and derivations thereof are for academic purposes only. LF is intended to be an implementation language. The performance of the implementation is evaluated in terms of practical metries such as the time needed to complete communication operations and the average time needed to service an interrupt.AFRIKAANSE OPSOMMING: Rekenaar ondersteunde verifikasietegnieke soos programmodellering, is onontbeerlik in die ontwikkeling van hoogs betroubare programmatuur. In die algemeen, aanvaar programme wat modelle toets eSP-agtige notasie as toevoer. Die meeste programme word egter in meer konvensionele imperatiewe programmeertale ontwikkel. Die vertaling vanuit die een paradigma na die ander is 'n moelike proses, wat baie ruimte laat vir foute. Indien daar uit die staanspoor in 'n proses gebaseerde taal geprogrammeer word, sou die verwydering tussen model en program makliker oorbrug kon word. Dit lei tot akkurater modelle en uiteindelik tot betroubaarder programmatuur. Die tesis ondersoek die definisie van 'n proses gebaseerde taal, wat gemik is op ingebedde programmatuur. Verder word die implementasie van 'n toepaslike vertaler en looptyd omgewing ook bespreek. Die taal, LF, is grotendeels gebaseer op Joyce, wat deur Brinch Hansen ontwikkel is. Joyce en op sy beurt LF, is verbeterings op ander esp verwante tale soos occam. 'n Voorbeeld hiervan is 'n selektiewe kommunikasieprimitief wat die gebruik van beide toevoer- en afvoerwagte ondersteun. Omdat 'n effektiewe implementasie nagestreef word, is die taalontwerp om so nadruklik moontlik te wees, sonder om strukture in te sluit wat oneffektief is om te implementeer. Sekuriteit was egter die oorheersende oorweging in die ontwerp van die taal en looptyd omgewing. Die vertaler lewer masjienkode, terwyl die meeste ander implementasies van eSP-agtige tale geinterpreteer word of ondersteun word as prosesse op 'n geskikte bedryfstelsel- die meeste eSP-agtige tale word slegs vir akademiese doeleindes aangewend. LF is by uitstek ontwerp as implementasie taal. Die evaluasie van die stelsel se werkverrigting is gedoen aan die hand van praktiese maatstawwe soos die tyd wat benodig word vir kommunikasie, sowel as die gemiddelde tyd benodig vir die hantering van onderbrekings