Fairness in systems based on multiparty interactions

In the context of the Multiparty Interaction Model, fairness is used to insure that an interaction that is enabled sufficiently often in a concurrent program will eventually be selected for execution. Unfortunately, this notion does not take conspiracies into account, i.e. situations in which an interaction never becomes enabled because of an unfortunate interleaving of independent actions; furthermore, eventual execution is usually too weak for practical purposes since this concept can only be used in the context of infinite executions. In this article, we present a new fairness notion, k-conspiracy-free fairness, that improves on others because it takes finite executions into account, alleviates conspiracies that are not inherent to a program, and k may be set a priori to control its goodness to address the above-mentioned problems.Ministerio de Ciencia y Tecnología TIC-2000-1106-C02-01Ministerio de Ciencia y Tecnología FIT-150100-2001-78Ministerio de Ciencia y Tecnología TAMANSI PCB-02-00

Generating non-conspiratorial executions

Avoiding conspiratorial executions is useful for debugging, model checking or refinement, and helps implement several wellknown problems in faulty environments; furthermore, avoiding non-equivalence robust executions prevents conflicting observations in a distributed setting from occurring. Our results prove that scheduling pairs of states and transitions in a strongly fair manner suf-fices to prevent conspiratorial executions; we then establish a formal connection between conspiracies and equivalence robustness; finally, we present a transformation scheme to implement our results and show how to build them into a well-known distributed scheduler. Previous results were applicable to a subset of systems only, just attempted to characterise potential conspiracies, or were tightly bound up with a particular interaction model.Comisión Interministerial de Ciencia y Tecnología TIC2003-02737-C0

Strong fairness and ultra metrics

AbstractWe answer an open question of Costa and Hennessy and present a characterization of the infinite fair computations in finite labeled transition systems—without any structure of the states—as cluster points in metric spaces. This technique is applied to reduce the logical complexity of several known fairness concepts from Π03 to Π02 and from Σ11 to Π03, respectively

Decidability Issues for Petri Nets

This is a survey of some decidability results for Petri nets, covering the last three decades. The presentation is structured around decidability of specific properties, various behavioural equivalences and finally the model checking problem for temporal logics

Concurrent systems and inevitability

AbstractConcurrent systems viewed as partially ordered sets of states are considered. A property of system states is called inevitable, if the system will eventually reach a state with this property. This notion is discussed within the partial order framework

Liveliness and fairness in non-deterministic environments

El problema de la vivacidad y la selección justa surge en el contexto de los sistemas con ejecuciones no deterministas. El concepto de selección completamente justa ´ sirve para garantizar que todos los elementos que se habilitan infinitamente a menudo se ejecutan infinitamente a menudo. Esta noción de selección presenta dos anomalías: la finitud justa y las conspiraciones. Este articulo se centra en la selección justa de interacciones en sistemas basados en ´ interacciones entre múltiples participantes ´ y presenta una nueva noción llamada ´ selección completamente ´ k–justa cuya principal ventaja sobre otras propuestas es que da solución a las dos anomalías de forma simultanea. Para ello, hemos descrito un marco de trabajo teórico para caracterizar los sistemas ´ basados en interacciones entre múltiples participantes que hace independiente el criterio de selección del lenguaje de programación . También presentamos un algoritmo general para implementar ´ la selección completamente ´ k–justa de interacciones que no requiere acceder al estado local de los procesos del sistema.The problem of liveliness and fair selection arises in the context of systems with executing non-deterministic tions. The concept of completely fair selection serves to ensure that all items that are enabled infinitely often are executed infinitely often. This notion of selection presents two anomalies: fair finitude and conspiracies. East The article focuses on the fair selection of interactions in systems based on multi-participant interactions and introduces a new notion called completely k-fair selection. whose main advantage over other proposals is that it solves the two anomalies simultaneously. To do this, we have described a theoretical framework to characterize the systems based on interactions between multiple participants that makes the selection criteria independent tion of the programming language. We also present a general algorithm to implement the completely k-fair selection of interactions that does not require access to the local state of system processes

Vivacidad y justicia en entornos no deterministas

El problema de la vivacidad y la selección justa surge en el contexto de los sistemas con ejecuciones no determinadas. El concepto de selección completamente justa sirve para garantizar que todos los elementos  que se habilitan infinitamente a menudo se ejecutan infinitamente a menudo.Palabras clave: Sistema distribuidos, Interacciones entre múltiples participantes, vivacidad, selección justa