Analysing Mutual Exclusion using Process Algebra with Signals

In contrast to common belief, the Calculus of Communicating Systems (CCS) and similar process algebras lack the expressive power to accurately capture mutual exclusion protocols without enriching the language with fairness assumptions. Adding a fairness assumption to implement a mutual exclusion protocol seems counter-intuitive. We employ a signalling operator, which can be combined with CCS, or other process calculi, and show that this minimal extension is expressive enough to model mutual exclusion: we confirm the correctness of Peterson's mutual exclusion algorithm for two processes, as well as Lamport's bakery algorithm, under reasonable assumptions on the underlying memory model. The correctness of Peterson's algorithm for more than two processes requires stronger, less realistic assumptions on the underlying memory model.Comment: In Proceedings EXPRESS/SOS 2017, arXiv:1709.0004

Justness: A Completeness Criterion for Capturing Liveness Properties (Extended Abstract)

This paper poses that transition systems constitute a good model of distributed systems only in combination with a criterion telling which paths model complete runs of the represented systems. Among such criteria, progress is too weak to capture relevant liveness properties, and fairness is often too strong; for typical applications we advocate the intermediate criterion of justness. Previously, we proposed a definition of justness in terms of an asymmetric concurrency relation between transitions. Here we define such a concurrency relation for the transition systems associated to the process algebra CCS as well as its extensions with broadcast communication and signals, thereby making these process algebras suitable for capturing liveness properties requiring justness.Comment: An extended abstract of this paper appears in Proc. FoSSaCS'1

Modelling Mutual Exclusion in a Process Algebra with Time-outs

I show that in a standard process algebra extended with time-outs one can correctly model mutual exclusion in such a way that starvation-freedom holds without assuming fairness or justness, even when one makes the problem more challenging by assuming memory accesses to be atomic. This can be achieved only when dropping the requirement of speed independence.Comment: arXiv admin note: text overlap with arXiv:2008.1335

Enabling Preserving Bisimulation Equivalence

Most fairness assumptions used for verifying liveness properties are criticised for being too strong or unrealistic. On the other hand, justness, arguably the minimal fairness assumption required for the verification of liveness properties, is not preserved by classical semantic equivalences, such as strong bisimilarity. To overcome this deficiency, we introduce a finer alternative to strong bisimilarity, called enabling preserving bisimilarity. We prove that this equivalence is justness-preserving and a congruence for all standard operators, including parallel composition

Reactive temporal logic

Whereas standard treatments of temporal logic are adequate for closed systems, having no run-time interactions with their environment, they fall short for reactive systems, interacting with their environments through synchronisation of actions. This paper introduces reactive temporal logic, a form of temporal logic adapted for the study of reactive systems. I illustrate its use by applying it to formulate definitions of a fair scheduler, and of a correct mutual exclusion protocol. Previous definitions of these concepts were conceptually much more involved or less precise, leading to debates on whether or not a given protocol satisfies the implicit requirements.Comment: In Proceedings EXPRESS/SOS 2020, arXiv:2008.1241

O Conceito de Justiça na Teoria dos Stakeholders: Uma Revisão Sistemática de Literatura

In strategic management, the Stakeholder Theory proclaims that in order to achieve better performance and sustainable competitive advantage, the organization has to treat each of its stakeholders fairly. Hence, the concept of justice becomes relevant in assessing the effectiveness of managerial decisions and is ingrained in the Stakeholder Theory literature. This paper aims to examine how the notion of justice is conceptualized and applied in the Stakeholder Theory literature; and to propose new avenues of research regarding the interconnections between these two subjects. We present a systematic literature review to synthesize the research in the area. A careful screening held in April 2019, resulted in 75 papers published in 35 journals from 1999 to 2019. The results were presented in two phases. First, in the form of a descriptive and bibliometric analysis of the selected papers. Second, by reviewing those papers, we offer a framework of how the notion of justice has been conceptualized and applied in the Stakeholder Theory literature. Finally, we propose an agenda for future research regarding the interconnection between justice and Stakeholder Theory.Na gestão estratégica, a Teoria dos Stakeholders indica que, para alcançar melhor desempenho e vantagem competitiva sustentável, a organização deve tratar cada uma das partes interessadas de maneira justa. Nesse sentido, o conceito de justiça se torna relevante na avaliação da eficácia das decisões gerenciais e está enraizado na literatura da Teoria dos Stakeholders. Este artigo tem como objetivo examinar como a ideia de justiça é conceitualizada e aplicada na literatura da Teoria dos Stakeholders, e propor novos direcionamentos de pesquisas futuras sobre as interconexões entre esses dois temas. Apresentamos uma revisão sistemática da literatura para sintetizar a pesquisa na área. Uma triagem em diferentes etapas, resultou em 75 artigos publicados em 35 revistas de 1999 a 2019. Os resultados foram apresentados em duas fases. Primeiro, na forma de uma análise descritiva e bibliométrica dos trabalhos selecionados. Segundo, revisando esses documentos, oferecemos uma estrutura de como a noção de justiça foi conceitualizada e aplicada na literatura da Teoria dos Stakeholders. Por fim, propomos uma agenda para pesquisas futuras sobre a interconexão entre justiça e a Teoria dos Stakeholders