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In 1997, Henry Lieberman stated that debugging is the dirty little secret of computer science. Since then, several promising debugging technologies have been developed such as back-in-time debuggers and automatic fault localization methods. However, the last study about the state-of-the-art in debugging is still more than 15 years old and so it is not clear whether these new approaches have been applied in practice or not. For that reason, we investigate the current state of debugging in a comprehensive study. First, we review the available literature and learn about current approaches and study results. Second, we observe several professional developers while debugging and interview them about their experiences. Third, we create a questionnaire that serves as the basis for a larger online debugging survey. Based on these results, we present new insights into debugging practice that help to suggest new directions for future research.
Distributed applications are hard to debug because timing-dependent network communication is a source of non-deterministic behavior. Current approaches to debug non deterministic failures include post-mortem debugging as well as record and replay. However, the first impairs system performance to gather data, whereas the latter requires developers to understand the timing-dependent communication at a lower level of abstraction than they develop at. Furthermore, both approaches require intrusive core library modifications to gather data from live systems. In this paper, we present the Peek-At-Talk debugger for investigating non-deterministic failures with low overhead in a systematic, top-down method, with a particular focus on tool-building issues in the following areas: First, we show how our debugging framework Path Tools guides developers from failures to their root causes and gathers run-time data with low overhead. Second, we present Peek-At-Talk, an extension to our Path Tools framework to record non-deterministic communication and refine behavioral data that connects source code with network events. Finally, we scope changes to the core library to record network communication without impacting other network applications.
Making the domain tangible
(2017)
Programmers collaborate continuously with domain experts to explore the problem space and to shape a solution that fits the users’ needs. In doing so, all parties develop a shared vocabulary, which is above all a list of named concepts and their relationships to each other. Nowadays, many programmers favor object-oriented programming because it allows them to directly represent real-world concepts and interactions from the vocabulary as code. However, when existing domain data is not yet represented as objects, it becomes a challenge to initially bring existing domain data into object-oriented systems and to keep the source code readable. While source code might be comprehensible to programmers, domain experts can struggle, given their non-programming background. We present a new approach to provide a mapping of existing data sources into the object-oriented programming environment. We support keeping the code of the domain model compact and readable while adding implicit means to access external information as internal domain objects. This should encourage programmers to explore different ways to build the software system quickly. Eventually, our approach fosters communication with the domain experts, especially at the beginning of a project. When the details in the problem space are not yet clear, the source code provides a valuable, tangible communication artifact.
Die Komplexität heutiger Geschäftsabläufe und die Menge der zu verwaltenden Daten stellen hohe Anforderungen an die Entwicklung und Wartung von Geschäftsanwendungen. Ihr Umfang entsteht unter anderem aus der Vielzahl von Modellentitäten und zugehörigen Nutzeroberflächen zur Bearbeitung und Analyse der Daten. Dieser Bericht präsentiert neuartige Konzepte und deren Umsetzung zur Vereinfachung der Entwicklung solcher umfangreichen Geschäftsanwendungen. Erstens: Wir schlagen vor, die Datenbank und die Laufzeitumgebung einer dynamischen objektorientierten Programmiersprache zu vereinen. Hierzu organisieren wir die Speicherstruktur von Objekten auf die Weise einer spaltenorientierten Hauptspeicherdatenbank und integrieren darauf aufbauend Transaktionen sowie eine deklarative Anfragesprache nahtlos in dieselbe Laufzeitumgebung. Somit können transaktionale und analytische Anfragen in derselben objektorientierten Hochsprache implementiert werden, und dennoch nah an den Daten ausgeführt werden. Zweitens: Wir beschreiben Programmiersprachkonstrukte, welche es erlauben, Nutzeroberflächen sowie Nutzerinteraktionen generisch und unabhängig von konkreten Modellentitäten zu beschreiben. Um diese abstrakte Beschreibung nutzen zu können, reichert man die Domänenmodelle um vormals implizite Informationen an. Neue Modelle müssen nur um einige Informationen erweitert werden um bereits vorhandene Nutzeroberflächen und -interaktionen auch für sie verwenden zu können. Anpassungen, die nur für ein Modell gelten sollen, können unabhängig vom Standardverhalten, inkrementell, definiert werden. Drittens: Wir ermöglichen mit einem weiteren Programmiersprachkonstrukt die zusammenhängende Beschreibung von Abläufen der Anwendung, wie z.B. Bestellprozesse. Unser Programmierkonzept kapselt Nutzerinteraktionen in synchrone Funktionsaufrufe und macht somit Prozesse als zusammenhängende Folge von Berechnungen und Interaktionen darstellbar. Viertens: Wir demonstrieren ein Konzept, wie Endnutzer komplexe analytische Anfragen intuitiver formulieren können. Es basiert auf der Idee, dass Endnutzer Anfragen als Konfiguration eines Diagramms sehen. Entsprechend beschreibt ein Nutzer eine Anfrage, indem er beschreibt, was sein Diagramm darstellen soll. Nach diesem Konzept beschriebene Diagramme enthalten ausreichend Informationen, um daraus eine Anfrage generieren zu können. Hinsichtlich der Ausführungsdauer sind die generierten Anfragen äquivalent zu Anfragen, die mit konventionellen Anfragesprachen formuliert sind. Das Anfragemodell setzen wir in einem Prototypen um, der auf den zuvor eingeführten Konzepten aufsetzt.
Programmers make many changes to the program to eventually find a good solution for a given task. In this course of change, every intermediate development state can of value, when, for example, a promising ideas suddenly turn out inappropriate or the interplay of objects turns out more complex than initially expected before making changes. Programmers would benefit from tool support that provides immediate access to source code and run-time of previous development states of interest. We present IDE extensions, implemented for Squeak/Smalltalk, to preserve, retrieve, and work with this information. With such tool support, programmers can work without worries because they can rely on tools that help them with whatever their explorations will reveal. They no longer have to follow certain best practices only to avoid undesired consequences of changing code.
Virtual machine (VM) implementations are made of intricately intertwined subsystems, interacting largely through implicit dependencies. As the degree of crosscutting present in VMs is very high, VM implementations exhibit significant internal complexity. This study proposes an architecture approach for VMs that regards a VM as a composite of service modules coordinated through explicit bidirectional interfaces. Aspect-oriented programming techniques are used to establish these interfaces, to coordinate module interaction, and to declaratively express concrete VM architectures. A VM architecture description language is presented in a case study, illustrating the application of the proposed architectural principles.
Use-cases are considered an integral part of most contemporary development processes since they describe a software system's expected behavior from the perspective of its prospective users. However, the presence of and traceability to use-cases is increasingly lost in later more code-centric development activities. Use-cases, being well-encapsulated at the level of requirements descriptions, eventually lead to crosscutting concerns in system design and source code. Tracing which parts of the system contribute to which use-cases is therefore hard and so limits understandability.
In this paper, we propose an approach to making use-cases first-class entities in both the programming language and the runtime environment. Having use-cases present in the code and the running system will allow developers, maintainers, and operators to easily associate their units of work with what matters to the users. We suggest the combination of use-cases, acceptance tests, and dynamic analysis to automatically associate source code with use-cases. We present UseCasePy, an implementation of our approach to use-case-centered development in Python, and its application to the Django Web framework.
Context-oriented programming (COP) provides dedicated support for defining and composing variations to a basic program behavior. A variation, which is defined within a layer, can be de-/activated for the dynamic extent of a code block. While this mechanism allows for control flow-specific scoping, expressing behavior adaptations can demand alternative scopes. For instance, adaptations can depend on dynamic object structure rather than control flow. We present scenarios for behavior adaptation and identify the need for new scoping mechanisms. The increasing number of scoping mechanisms calls for new language abstractions representing them. We suggest to open the implementation of scoping mechanisms so that developers can extend the COP language core according to their specific needs. Our open implementation moves layer composition into objects to be affected and with that closer to the method dispatch to be changed. We discuss the implementation of established COP scoping mechanisms using our approach and present new scoping mechanisms developed for our enhancements to Lively Kernel.