On the Decidability of Non Interference over Unbounded Petri Nets

Non-interference, in transitive or intransitive form, is defined here over unbounded (Place/Transition) Petri nets. The definitions are adaptations of similar, well-accepted definitions introduced earlier in the framework of labelled transition systems. The interpretation of intransitive non-interference which we propose for Petri nets is as follows. A Petri net represents the composition of a controlled and a controller systems, possibly sharing places and transitions. Low transitions represent local actions of the controlled system, high transitions represent local decisions of the controller, and downgrading transitions represent synchronized actions of both components. Intransitive non-interference means the impossibility for the controlled system to follow any local strategy that would force or dodge synchronized actions depending upon the decisions taken by the controller after the last synchronized action. The fact that both language equivalence and bisimulation equivalence are undecidable for unbounded labelled Petri nets might be seen as an indication that non-interference properties based on these equivalences cannot be decided. We prove the opposite, providing results of decidability of non-interference over a representative class of infinite state systems.Comment: In Proceedings SecCo 2010, arXiv:1102.516

Dynamic Clusters

Globalization has had an enormous impact on traditional industrial structures. It seems almost the case that everything is everywhere the same. And yet, in reality, some regions in a single industrialized country enjoy rapid economic growth while others are downsizing or stagnating. Thus there must be some remaining regional competitive advantages—even in the “Age of Globalization.” This paper engages in a quest to discover what these new “locational” factors might be and how and why they are necessary in creating a dynamic cluster of regional growth. In doing so, we try to link agglomeration advantages of the new economic geography with competitive advantages of Porter’s cluster theory. But we also go beyond these approaches and add further regional growth factors such as creativity or diversity. Using data that paint a comprehensive picture of industry and regional development in Germany we try to find empirical evidence for our approach. A case study from the automobile industry – one of the leading industries in Germany – completes our picture of dynamic clusters.Cluster, Regional Growth, Innovation, Creativity

The effect of (non-)competing brokers on the quality and price of differentiated internet services

Price war, as an important factor in undercutting competitors and attracting customers, has spurred considerable work that analyzes such conflict situation. However, in most of these studies, quality of service (QoS), as an important decision-making criterion, has been neglected. Furthermore, with the rise of service-oriented architectures, where players may offer different levels of QoS for different prices, more studies are needed to examine the interaction among players within the service hierarchy. In this paper, we present a new approach to modeling price competition in (virtualized) service-oriented architectures, where there are multiple service levels. In our model, brokers, as intermediaries between end-users and service providers, offer different QoS by adapting the service that they obtain from lower-level providers so as to match the demands of their clients to the services of providers. To maximize profit, players, i.e. providers and brokers, at each level compete in a Bertrand game while they offer different QoS. To maintain an oligopoly market, we then describe underlying dynamics which lead to a Bertrand game with price constraints at the providers’ level. We also study cooperation among a subset of brokers. Numerical simulations demonstrate the behavior of brokers and providers and the effect of price competition on their market shares.Accepted manuscrip

Immigrants at New Destinations: How They Fare and Why

Using matched employer-employee data, we identify the determinants of immigrants’ earnings in the Portuguese labor market. Results previously reported for countries with a long tradition of hosting migrants are also valid in a new destination country. Two-thirds of the gap is attributable to match-specific and employer characteristics. Occupational downgrading and segregation into low-wage workplaces are two major causes behind the wage gap.immigrants' earnings, workplace concentration of immigrants, matched employer-employee data