348 research outputs found
OSS architecture for mixed-criticality systems – a dual view from a software and system engineering perspective
Computer-based automation in industrial appliances led to a growing number of
logically dependent, but physically separated embedded control units per
appliance. Many of those components are safety-critical systems, and require
adherence to safety standards, which is inconsonant with the relentless demand
for features in those appliances. Features lead to a growing amount of control
units per appliance, and to a increasing complexity of the overall software
stack, being unfavourable for safety certifications. Modern CPUs provide means
to revise traditional separation of concerns design primitives: the consolidation
of systems, which yields new engineering challenges that concern the entire
software and system stack.
Multi-core CPUs favour economic consolidation of formerly separated
systems with one efficient single hardware unit. Nonetheless, the system
architecture must provide means to guarantee the freedom from interference
between domains of different criticality. System consolidation demands for
architectural and engineering strategies to fulfil requirements (e.g., real-time
or certifiability criteria) in safety-critical environments.
In parallel, there is an ongoing trend to substitute ordinary proprietary base
platform software components by mature OSS variants for economic and
engineering reasons. There are fundamental differences of processual properties
in development processes of OSS and proprietary software. OSS in
safety-critical systems requires development process assessment techniques to
build an evidence-based fundament for certification efforts that is based upon
empirical software engineering methods.
In this thesis, I will approach from both sides: the software and system
engineering perspective. In the first part of this thesis, I focus on the
assessment of OSS components: I develop software engineering techniques
that allow to quantify characteristics of distributed OSS development
processes. I show that ex-post analyses of software development processes can
be used to serve as a foundation for certification efforts, as it is required
for safety-critical systems.
In the second part of this thesis, I present a system architecture based on
OSS components that allows for consolidation of mixed-criticality systems
on a single platform. Therefore, I exploit virtualisation extensions of modern
CPUs to strictly isolate domains of different criticality. The proposed
architecture shall eradicate any remaining hypervisor activity in order to
preserve real-time capabilities of the hardware by design, while
guaranteeing strict isolation across domains.ComputergestĂĽtzte Automatisierung industrieller Systeme fĂĽhrt zu einer
wachsenden Anzahl an logisch abhängigen, aber physisch voneinander getrennten
Steuergeräten pro System. Viele der Einzelgeräte sind sicherheitskritische
Systeme, welche die Einhaltung von Sicherheitsstandards erfordern, was durch
die unermüdliche Nachfrage an Funktionalitäten erschwert wird. Diese führt zu
einer wachsenden Gesamtzahl an Steuergeräten, einhergehend mit wachsender
Komplexität des gesamten Softwarekorpus, wodurch Zertifizierungsvorhaben
erschwert werden. Moderne Prozessoren stellen Mittel zur VerfĂĽgung, welche es
ermöglichen, das traditionelle >Trennung von Belangen< Designprinzip zu
erneuern: die Systemkonsolidierung. Sie stellt neue ingenieurstechnische
Herausforderungen, die den gesamten Software und Systemstapel betreffen.
Mehrkernprozessoren begünstigen die ökonomische und effiziente Konsolidierung
vormals getrennter Systemen zu einer effizienten Hardwareeinheit. Geeignete
Systemarchitekturen müssen jedoch die Rückwirkungsfreiheit zwischen Domänen
unterschiedlicher Kritikalität sicherstellen. Die Konsolidierung erfordert
architektonische, als auch ingenieurstechnische Strategien um die Anforderungen
(etwa Echtzeit- oder Zertifizierbarkeitskriterien) in sicherheitskritischen
Umgebungen erfüllen zu können.
Zunehmend werden herkömmliche proprietär entwickelte Basisplattformkomponenten
aus ökonomischen und technischen Gründen vermehrt durch ausgereifte OSS
Alternativen ersetzt. Jedoch hindern fundamentale Unterschiede bei prozessualen
Eigenschaften des Entwicklungsprozesses bei OSS den Einsatz in
sicherheitskritischen Systemen. Dieser erfordert Techniken, welche es erlauben
die Entwicklungsprozesse zu bewerten um ein evidenzbasiertes Fundament fĂĽr
Zertifizierungsvorhaben basierend auf empirischen Methoden des Software
Engineerings zur VerfĂĽgung zu stellen.
In dieser Arbeit nähere ich mich von beiden Seiten: der Softwaretechnik, und
der Systemarchitektur. Im ersten Teil befasse ich mich mit der Beurteilung von
OSS Komponenten: Ich entwickle Softwareanalysetechniken, welche es
ermöglichen, prozessuale Charakteristika von verteilten OSS
Entwicklungsvorhaben zu quantifizieren. Ich zeige, dass rĂĽckschauende Analysen
des Entwicklungsprozess als Grundlage fĂĽr Softwarezertifizierungsvorhaben
genutzt werden können.
Im zweiten Teil dieser Arbeit widme ich mich der Systemarchitektur. Ich stelle
eine OSS-basierte Systemarchitektur vor, welche die Konsolidierung von
Systemen gemischter Kritikalität auf einer alleinstehenden Plattform
ermöglicht. Dazu nutze ich Virtualisierungserweiterungen moderner Prozessoren
aus, um die Hardware in strikt voneinander isolierten Rechendomänen unterschiedlicher
Kritikalität unterteilen zu können. Die vorgeschlagene Architektur soll jegliche
Betriebsstörungen des Hypervisors beseitigen, um die Echtzeitfähigkeiten der
Hardware bauartbedingt aufrecht zu erhalten, während strikte Isolierung
zwischen Domänen stets sicher gestellt ist
Modeling User-Affected Software Properties for Open Source Software Supply Chains
Background: Open Source Software development community relies heavily on users of the software and contributors outside of the core developers to produce top-quality software and provide long-term support. However, the relationship between a software and its contributors in terms of exactly how they are related through dependencies and how the users of a software affect many of its properties are not very well understood.
Aim: My research covers a number of aspects related to answering the overarching question of modeling the software properties affected by users and the supply chain structure of software ecosystems, viz. 1) Understanding how software usage affect its perceived quality; 2) Estimating the effects of indirect usage (e.g. dependent packages) on software popularity; 3) Investigating the patch submission and issue creation patterns of external contributors; 4) Examining how the patch acceptance probability is related to the contributors\u27 characteristics. 5) A related topic, the identification of bots that commit code, aimed at improving the accuracy of these and other similar studies was also investigated.
Methodology: Most of the Research Questions are addressed by studying the NPM ecosystem, with data from various sources like the World of Code, GHTorrent, and the GiHub API. Different supervised and unsupervised machine learning models, including Regression, Random Forest, Bayesian Networks, and clustering, were used to answer appropriate questions.
Results: 1) Software usage affects its perceived quality even after accounting for code complexity measures. 2) The number of dependents and dependencies of a software were observed to be able to predict the change in its popularity with good accuracy. 3) Users interact (contribute issues or patches) primarily with their direct dependencies, and rarely with transitive dependencies. 4) A user\u27s earlier interaction with the repository to which they are contributing a patch, and their familiarity with related topics were important predictors impacting the chance of a pull request getting accepted. 5) Developed BIMAN, a systematic methodology for identifying bots.
Conclusion: Different aspects of how users and their characteristics affect different software properties were analyzed, which should lead to a better understanding of the complex interaction between software developers and users/ contributors
Performance Implications of Stage-Wise Lead User Participation in Software Development Problem Solving
The problem-solving view of new product development sees the innovation process as a series of problem-solving loops broken down into three stages: problem detection, analysis and removal. We link this framework with lead user-driven innovation regarding software and show that effort by lead users (LUs) in each stage of the innovation problem solving process is, in varying degrees, associated with the source code’s quality, the productivity of the development process and the software’s popularity. We also test whether front loading the problem solving process is associated with development performance and we find that front loading is associated with increased code quality but decreased development productivity. Empirical tests are carried out with data from open source software projects. Findings potentially impact the design and management of online communities to help product development
On Wasted Contributions: Understanding the Dynamics of Contributor-Abandoned Pull Requests
Pull-based development has enabled numerous volunteers to contribute to
open-source projects with fewer barriers. Nevertheless, a considerable amount
of pull requests (PRs) with valid contributions are abandoned by their
contributors, wasting the effort and time put in by both the contributors and
maintainers. To better understand the underlying dynamics of
contributor-abandoned PRs, we conduct a mixed-methods study using both
quantitative and qualitative methods. We curate a dataset consisting of 265,325
PRs including 4,450 abandoned ones from ten popular and mature GitHub projects
and measure 16 features characterizing PRs, contributors, review processes, and
projects. Using statistical and machine learning techniques, we find that
complex PRs, novice contributors, and lengthy reviews have a higher probability
of abandonment and the rate of PR abandonment fluctuates alongside the
projects' maturity or workload. To identify why contributors abandon their PRs,
we also manually examine a random sample of 354 abandoned PRs. We observe that
the most frequent abandonment reasons are related to the obstacles faced by
contributors, followed by the hurdles imposed by maintainers during the review
process. Finally, we survey the top core maintainers of the studied projects to
understand their perspectives on dealing with PR abandonment and on our
findings.Comment: Manuscript accepted for publication in ACM Transactions on Software
Engineering and Methodology (TOSEM
Pull request latency explained:an empirical overview
Pull request latency evaluation is an essential application of effort evaluation in the pull-based development scenario. It can help the reviewers sort the pull request queue, remind developers about the review processing time, speed up the review process and accelerate software development. There is a lack of work that systematically organizes the factors that affect pull request latency. Also, there is no related work discussing the differences and variations in characteristics in different scenarios and contexts. In this paper, we collected relevant factors through a literature review approach. Then we assessed their relative importance in five scenarios and six different contexts using the mixed-effects linear regression model. The most important factors differ in different scenarios. The length of the description is most important when pull requests are submitted. The existence of comments is most important when closing pull requests, using CI tools, and when the contributor and the integrator are different. When there exist comments, the latency of the first comment is the most important. Meanwhile, the influence of factors may change in different contexts. For example, the number of commits in a pull request has a more significant impact on pull request latency when closing than submitting due to changes in contributions brought about by the review process. Both human and bot comments are positively correlated with pull request latency. In contrast, the bot’s first comments are more strongly correlated with latency, but the number of comments is less correlated. Future research and tool implementation needs to consider the impact of different contexts. Researchers can conduct related studies based on our publicly available datasets and replication scripts
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