Undecidability of accordance for open systems with unbounded message queues

We study asynchronously communicating open systems modeled as Petri nets with an interface. An accordance preorder describes when one open system can be safely replaced by another open system without aecting some behavioral property of the overall system. Although accordance is decidable for several behavioral properties if we assume a previously known bound on the maximal number of pending messages, we show that it is not decidable without this assumption. Keywords: Petri nets, open nets, accordance preorder, theory of computatio

Undecidability of accordance for open systems with unbounded message queues

We study asynchronously communicating open systems modeled as Petri nets with an interface. An accordance preorder describes when one open system can be safely replaced by another open system without aecting some behavioral property of the overall system. Although accordance is decidable for several behavioral properties if we assume a previously known bound on the maximal number of pending messages, we show that it is not decidable without this assumption. Keywords: Petri nets, open nets, accordance preorder, theory of computatio

I Would if I Could: Precarious Employment and Childbearing Intentions in Italy

This paper carries out an investigation into the socio-economic determinants of childbearing decisions made by couples in Italy. The analysis accounts for the characteristics of both possible parents. Our results do not support established theoretical predictions according to which the increase in the opportunity cost of motherhood connected to higher female labour participation is responsible for the fall in fertility. On the contrary, the instability of women’s work status (i.e. having occasional, precarious, and low-paid positions) is revealed as a significant dissuasive factor in the decision to have children. Couples in which there is an unemployed woman are less likely to plan childbearing as well. Other relevant explanatory variables are women’s age, men’s work status and education, women’s citizenship, marital status and perceived economic wellbeing.Fertility, family planning, parenthood, childbearing, participation, job instability, precarious employment, Italy.

Decidability and coincidence of equivalences for concurrency

There are two fundamental problems concerning equivalence relations in con-currency. One is: for which system classes is a given equivalence decidable? The second is: when do two equivalences coincide? Two well-known equivalences are history preserving bisimilarity (hpb) and hereditary history preserving bisimi-larity (hhpb). These are both ‘independence ’ equivalences: they reflect causal dependencies between events. Hhpb is obtained from hpb by adding a ‘back-tracking ’ requirement. This seemingly small change makes hhpb computationally far harder: hpb is well-known to be decidable for finite-state systems, whereas the decidability of hhpb has been a renowned open problem for several years; only recently it has been shown undecidable. The main aim of this thesis is to gain insights into the decidability problem for hhpb, and to analyse when it coincides with hpb; less technically, we might say, to analyse the power of the interplay between concurrency, causality, and conflict. We first examine the backtracking condition, and see that it has two dimen

Aeolus: a Component Model for the Cloud

International audienceWe introduce the Aeolus component model, which is specifically designed to capture realistic scenarii arising when configuring and deploying distributed applications in the so-called cloud environments, where interconnected components can be deployed on clusters of heterogeneous virtual machines, which can be in turn created, destroyed, and connected on-the-fly. The full Aeolus model is able to describe several component characteristics such as dependencies, conflicts, non-functional requirements (replication requests and load limits), as well as the fact that component interfaces to the world might vary depending on the internal component state. When the number of components needed to build an application grows, it becomes important to be able to automate activities such as deployment and reconfiguration. This correspond, at the level of the model, to the ability to decide whether a desired target system configuration is reachable, which we call the achievability problem, and producing a path to reach it. In this work we show that the achievability problem is undecidable for the full Aeolus model, a strong limiting result for automated configuration in the cloud. We also show that the problem becomes decidable, but Ackermann-hard, as soon as one drops non-functional requirements. Finally, we provide a polynomial time algorithm for the further restriction of the model where support for inter-component conflicts is also removed

Foundations of Software Science and Computation Structures

This open access book constitutes the proceedings of the 24th International Conference on Foundations of Software Science and Computational Structures, FOSSACS 2021, which was held during March 27 until April 1, 2021, as part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2021. The conference was planned to take place in Luxembourg and changed to an online format due to the COVID-19 pandemic. The 28 regular papers presented in this volume were carefully reviewed and selected from 88 submissions. They deal with research on theories and methods to support the analysis, integration, synthesis, transformation, and verification of programs and software systems

Modeling Interaction-Oriented Architectures using Choreographies

The Software architecture of a system can be regarded as a consistent set of views to describe the system. This paper focuses on the interaction between components in a system. These can be modeled as choreographies, capturing all allowed interactions between the components. In this paper, we show that it is feasible to analyze a composed set of these choreographies: a tree of choreographies in which each member may refer to another. The two major components of the analysis are correctness by structure: a choreography needs to follow strict rules to guarantee soundness. Otherwise, the choreography is transformed into a Petri net which is checked by an external tool. This paper shows the theoretical techniques to verify a composed choreography, and implements the solutions into a single educational modeler tool: INORA2

Public sexuality: a contemporary history of gay images and identity

This study is an examination of the public imaging of gay men and lesbians during the latter part of the twentieth and early part of the twenty-first centuries. The study looks at public imaging as it is performed in the service of the political aims of gay people, with an eye towards the kinds of tensions and erasures that occur when one monolithic identity is promoted. Through these examinations, I create a kind of contemporary history of the gay political rights movement. In the study, I examine theoretical approaches to identity from several postmodern theorists and then use these approaches to support my work in the three chapters. In each chapter I focus on one site of gay identity performances: Southern Decadence in New Orleans, the murder of Matthew Shepard, and the decriminalization of sodomy. At each site, I examine the event, the various identities presented, and the tensions and erasures that result from the specific identity performances. In conclusion, I envision a political movement which is inclusive of multiple identities – not just those which fit a predetermined conservative public presentation