New Directions in Programming Environments: Extensible Software

If we want software that can be adapted to our needs on the long run, extensibility is a main requirement. For a long time, extensibility has been in conflict with stability and/or efficiency. This situation has changed with recent software technologies. Thetools provided by software technology however must be complementedby a design which exploits their facilities for extensibility. We illustrate this using Voyager, a portable data analysis system basedon Oberon

The design and application of an extensible operating system

Tanenbaum, A.S. [Promotor

Supporting the evolution of software

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Resilience of an embedded architecture using hardware redundancy

In the last decade the dominance of the general computing systems market has being replaced by embedded systems with billions of units manufactured every year. Embedded systems appear in contexts where continuous operation is of utmost importance and failure can be profound. Nowadays, radiation poses a serious threat to the reliable operation of safety-critical systems. Fault avoidance techniques, such as radiation hardening, have been commonly used in space applications. However, these components are expensive, lag behind commercial components with regards to performance and do not provide 100% fault elimination. Without fault tolerant mechanisms, many of these faults can become errors at the application or system level, which in turn, can result in catastrophic failures. In this work we study the concepts of fault tolerance and dependability and extend these concepts providing our own definition of resilience. We analyse the physics of radiation-induced faults, the damage mechanisms of particles and the process that leads to computing failures. We provide extensive taxonomies of 1) existing fault tolerant techniques and of 2) the effects of radiation in state-of-the-art electronics, analysing and comparing their characteristics. We propose a detailed model of faults and provide a classification of the different types of faults at various levels. We introduce an algorithm of fault tolerance and define the system states and actions necessary to implement it. We introduce novel hardware and system software techniques that provide a more efficient combination of reliability, performance and power consumption than existing techniques. We propose a new element of the system called syndrome that is the core of a resilient architecture whose software and hardware can adapt to reliable and unreliable environments. We implement a software simulator and disassembler and introduce a testing framework in combination with ERA’s assembler and commercial hardware simulators

An architecture for interpreted dynamic object-oriented languages

e code refers to the representation of bytecodes as constant C arrays that are located in sharable text segments after compilation. Interoperability, application start-up and dynamic memory usage benefit from this representation. Indexed code threading addresses the performance problem with virtual instruction mapping (i.e. loading, decoding and invoking) by using a fast threaded instruction transfer. Unlike with standard code threading, virtual machine code remains compact and executable also with a non-threaded virtual machine emulator. A further performance boost is achieved with optimal virtual instruction ordering. This technique helps to cluster the native code implementing virtual instructions so that native instruction cache performance is increased. Finally, the efficiency problem involved with dynamic method lookup is alleviated with an inline caching scheme that is applicable with constant bytecode vectors. The scheme exploits type locality similar to polymorphic inline cac

Proposals for enhancement of the Ada programming language:a software engineering perspective

This thesis is a critique of the Ada 83 programming language with emphasis on the construction of reusable components and their composition, and more generally on programming "in the large". Ada 83's deficiencies in that area are first described, and then solutions are proposed to most of the problems. The main part of the thesis is a proposal for object-oriented extensions, making classes and objects with inheritance available through package and task types, as a very natural extension of Ada 83's task types. These proposals can be viewed as an alternative to Ada 9X's tagged types, with which a comparison is made

Proposals for Enhancement for the Ada Programming Language: A Software Engineering Perspective

For an abstract and an HTML version of the thesis, please visit http://lgl.epfl.ch/Team/MW/Ada-Extensions/Ada-Extensions.html</a