The practice of literate programming is not widespread because existing literate programming systems have some undesirable characteristics such as programming language and text processor dependence and lack of flexible tools for viewing and manipulation of the source file. This dissertation describes the literate programming system AOPS (Abstraction Oriented Programming System) which addresses both of these problems. AOPS is programming language and text processor independent literate programming system. AOPS tools include a hypertext browser, a lister with the ability to select what is presented and what is suppressed, and a filter to extract the program code from the AOPS source file. AOPS introduces the notion of a phantom abstraction that enhances the understandability of the literate program and when used in conjunction with the browser greatly extends the capabilities of AOPS. We also discuss how the design of AOPS supports extension of the concept of literate programming to encompass the entire software life cycle. Finally we describe an experiment which showed that literate programs contain more documentation than traditional programs. / Graduation date: 1993

There are three distinct processes that are predominant in models of flowing media with interacting components: advection, reaction, and diffusion. Collectively, these processes are typically modelled with partial differential equations (PDEs) known as advection-reaction-diffusion (ARD) equations.<p> To solve most PDEs in practice, approximation methods known as numerical methods are used. The method of lines is used to approximate PDEs with systems of ordinary differential equations (ODEs) by a process known as semi-discretization. ODEs are more readily analysed and benefit from well-developed numerical methods and software. Each term of an ODE that corresponds to one of the processes of an ARD equation benefits from particular mathematical properties in a numerical method. These properties are often mutually exclusive for many basic numerical methods.<p> A limitation to the widespread use of more complex numerical methods is that the development of the appropriate software to provide comparisons to existing numerical methods is not straightforward. Scientific and numerical software is often inflexible, motivating the development of a class of software known as problem-solving environments (PSEs). Many existing PSEs such as Matlab have solvers for ODEs and PDEs but lack specific features, beyond a scripting language, to readily experiment with novel or existing solution methods. The PSE developed during the course of this thesis solves ODEs known as initial-value problems, where only the initial state is fully known. The PSE is used to assess the performance of new numerical methods for ODEs that integrate each term of a semi-discretized ARD equation. This PSE is part of the PSE pythODE that uses object-oriented and software-engineering techniques to allow implementations of many existing and novel solution methods for ODEs with minimal effort spent on code modification and integration.<p> The new numerical methods use a commutator-free exponential Runge-Kutta (CFERK) method to solve the advection term of an ARD equation. A matrix exponential is used as the exponential function, but CFERK methods can use other numerical methods that model the flowing medium. The reaction term is solved separately using an explicit Runge-Kutta method because solving it along with the diffusion term can result in stepsize restrictions and hence inefficiency. The diffusion term is solved using a Runge-Kutta-Chebyshev method that takes advantage of the spatially symmetric nature of the diffusion process to avoid stepsize restrictions from a property known as stiffness. The resulting methods, known as Integrating-factor-based 2-additive Runge-Kutta methods, are shown to be able to find higher-accuracy solutions in less computational time than competing methods for certain challenging semi-discretized ARD equations. This demonstrates the practical viability both of using CFERK methods for advection and a 3-splitting in general.

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The goal of runtime verifi cation is to inspect the well-being of a system by employing a monitor during its execution. Such monitoring imposes cost in terms of resource utilization. Memory usage and predictability of monitor invocations are the key indicators of the quality of a monitoring solution, especially in the context of embedded systems. In this work, we propose a novel control-theoretic approach for coordinating time predictability and memory utilization in runtime monitoring of real-time embedded systems. In particular, we design a PID controller and four fuzzy controllers with di erent optimization control objectives. Our approach controls the frequency of monitor invocations by incorporating a bounded memory bu er that stores events which need to be monitored. The controllers attempt to improve time predictability, and maximize memory utilization, while ensuring the soundness of the monitor. Unlike existing approaches based on static analysis, our approach is scalable and well-suited for reactive systems that are required to react to stimuli from the environment in a timely fashion. Our experiments using two case studies (a laser beam stabilizer for aircraft tracking, and a Bluetooth mobile payment system) demonstrate the advantages of using controllers to achieve low variation in the frequency of monitor invocations, while maintaining maximum memory utilization in highly non-linear environments. In addition to this problem, the thesis presents a brief overview of our preceding work on runtime verifi cation.

In recent years, many aspect-oriented languages and methods have been proposed in the literature to support separation of concerns that can be spread throughout a software system and its components and to facilitate post-development and unpredictable system changes in the code of these systems. These languages and methods provide new abstraction and composition mechanisms to deal with some special concerns, which are called cross-cutting concerns. Cross-cutting concerns, by nature, encode structures that represent changes related to many different system modules, and are often difficult to understand. Also, the provision and support for metrics that can give quantitative estimates related to various software quality features had been a challenge. Because of the complexity and intricate relationships with the base code, techniques for more rigorous analysis are crucially needed to check whether, for instance, some aspects are interfering with other aspects in an undesirable way or not behaving according to the systems requirements and expected behaviour. In this thesis we advocate that by extending the metrics and analysis capabilities of current approaches, which are often restricted to code-level evaluations, we can (i) define an approach to analyze aspect-oriented systems based on design and architecture-level quality criteria and metrics, (ii) implement tool support for our approach and (iii) provided experimental support based on case studies indicating the usefulness and impact of the approach.

A Distributed Event-based System (DEBS) exhibits its desired behavior through its functional components collaborating with each other via event exchanging. Due to loose-coupling and flexibility, DEBS applications have become increasingly popular. Indeed, such systems are expected to appear in various application domains such as large-scale Internet applications and ubiquitous computing. Notwithstanding their popularity, current DEBS applications are still often developed in an informal process and are not modularized. On the individual event level, current DEBS developers can define what events a component can accept and publish, and, by registering event handlers, what action an event can trigger. Currently, developers lack structuring mechanisms for representing event interactions and dependencies in a modular way. While current research has made fruitful contributions to various aspects in the DEBS paradigm, such as, event delivery, event detection and composition, event visibility, its emphasis is on the individual event level. In this thesis, we advocate that by designing a new DEBS metamodel with extended behavioral interfaces and high-level structure mechanisms, we can (1) define an interface-based modular approach to model and design DEBS applications, (2) implement a prototype framework on a P2P network that provides built-in support to our proposed interface-based DEBS development, and (3) provide case studies illustrating the interface-based development process and the applicability of our proposed approach.

Using design patterns is a widely accepted method to improve software development. There are many benefits of the application of patterns claimed in the literature. The most cited claim is that design patterns can provide a common design vocabulary and therefore improve greatly communication between software designers. Most of the claims are supported by experiences reports of practitioners, but there is a lack of quantitative research concerning the actual application of design patterns and about the realization of the claimed benefits. In this paper we analyze the development process of over 1000 open source software projects using version control information. We explore this information to gain an insight into the differences of software development with and without design patters. (author's abstract) / Series: Working Papers on Information Systems, Information Business and Operations

Although markets are emerging for commercial off-the-shelf components (such as Sun JavaBeans), there are many barriers to widespread component adoption. This is due to the inherent `black-box' nature of software components: developers have no knowledge or control of the component's internal characteristics. Without source or design details, developers only have the component's interface, documentation and test results to answer important questions about reliability, proper use, behavior andperformance. The current best practice of specifying a component's capabilities by providing only the syntax and informal documentation is insufficient to assemble mission or safety-critical systems successfully. To address these problems we have developed a framework forcreating and analyzing the concise specifications of components and their related interfaces. The framework extends a formal model for software architecture descriptions to support the specification of a range of terms. With formal component specifications developers can use the framework to analyze the properties of individual components or of entire systems. Unlike other approaches, the formal basis and implementation of our framework enhance understanding and automates much of thecomponent analysis process.

In recent years, many aspect-oriented languages and methods have been proposed in the literature to support separation of concerns that can be spread throughout a software system and its components and to facilitate post-development and unpredictable system changes in the code of these systems. These languages and methods provide new abstraction and composition mechanisms to deal with some special concerns, which are called cross-cutting concerns. Cross-cutting concerns, by nature, encode structures that represent changes related to many different system modules, and are often difficult to understand. Also, the provision and support for metrics that can give quantitative estimates related to various software quality features had been a challenge. Because of the complexity and intricate relationships with the base code, techniques for more rigorous analysis are crucially needed to check whether, for instance, some aspects are interfering with other aspects in an undesirable way or not behaving according to the systems requirements and expected behaviour. In this thesis we advocate that by extending the metrics and analysis capabilities of current approaches, which are often restricted to code-level evaluations, we can (i) define an approach to analyze aspect-oriented systems based on design and architecture-level quality criteria and metrics, (ii) implement tool support for our approach and (iii) provided experimental support based on case studies indicating the usefulness and impact of the approach.

A Distributed Event-based System (DEBS) exhibits its desired behavior through its functional components collaborating with each other via event exchanging. Due to loose-coupling and flexibility, DEBS applications have become increasingly popular. Indeed, such systems are expected to appear in various application domains such as large-scale Internet applications and ubiquitous computing. Notwithstanding their popularity, current DEBS applications are still often developed in an informal process and are not modularized. On the individual event level, current DEBS developers can define what events a component can accept and publish, and, by registering event handlers, what action an event can trigger. Currently, developers lack structuring mechanisms for representing event interactions and dependencies in a modular way. While current research has made fruitful contributions to various aspects in the DEBS paradigm, such as, event delivery, event detection and composition, event visibility, its emphasis is on the individual event level. In this thesis, we advocate that by designing a new DEBS metamodel with extended behavioral interfaces and high-level structure mechanisms, we can (1) define an interface-based modular approach to model and design DEBS applications, (2) implement a prototype framework on a P2P network that provides built-in support to our proposed interface-based DEBS development, and (3) provide case studies illustrating the interface-based development process and the applicability of our proposed approach.