Impossibility of Gathering, a Certification

Recent advances in Distributed Computing highlight models and algorithms for autonomous swarms of mobile robots that self-organise and cooperate to solve global objectives. The overwhelming majority of works so far considers handmade algorithms and proofs of correctness. This paper builds upon a previously proposed formal framework to certify the correctness of impossibility results regarding distributed algorithms that are dedicated to autonomous mobile robots evolving in a continuous space. As a case study, we consider the problem of gathering all robots at a particular location, not known beforehand. A fundamental (but not yet formally certified) result, due to Suzuki and Yamashita, states that this simple task is impossible for two robots executing deterministic code and initially located at distinct positions. Not only do we obtain a certified proof of the original impossibility result, we also get the more general impossibility of gathering with an even number of robots, when any two robots are possibly initially at the same exact location.Comment: 10

A Certified Universal Gathering Algorithm for Oblivious Mobile Robots

We present a new algorithm for the problem of universal gathering mobile oblivious robots (that is, starting from any initial configuration that is not bivalent, using any number of robots, the robots reach in a finite number of steps the same position, not known beforehand) without relying on a common chirality. We give very strong guaranties on the correctness of our algorithm by proving formally that it is correct, using the COQ proof assistant. To our knowledge, this is the first certified positive (and constructive) result in the context of oblivious mobile robots. It demonstrates both the effectiveness of the approach to obtain new algorithms that are truly generic, and its managability since the amount of developped code remains human readable

Certified Universal Gathering in R2R^2 for Oblivious Mobile Robots

We present a unified formal framework for expressing mobile robots models, protocols, and proofs, and devise a protocol design/proof methodology dedicated to mobile robots that takes advantage of this formal framework. As a case study, we present the first formally certified protocol for oblivious mobile robots evolving in a two-dimensional Euclidean space. In more details, we provide a new algorithm for the problem of universal gathering mobile oblivious robots (that is, starting from any initial configuration that is not bivalent, using any number of robots, the robots reach in a finite number of steps the same position, not known beforehand) without relying on a common orientation nor chirality. We give very strong guaranties on the correctness of our algorithm by proving formally that it is correct, using the COQ proof assistant. This result demonstrates both the effectiveness of the approach to obtain new algorithms that use as few assumptions as necessary, and its manageability since the amount of developed code remains human readable.Comment: arXiv admin note: substantial text overlap with arXiv:1506.0160

Certified Impossibility Results for Byzantine-Tolerant Mobile Robots

We propose a framework to build formal developments for robot networks using the COQ proof assistant, to state and to prove formally various properties. We focus in this paper on impossibility proofs, as it is natural to take advantage of the COQ higher order calculus to reason about algorithms as abstract objects. We present in particular formal proofs of two impossibility results forconvergence of oblivious mobile robots if respectively more than one half and more than one third of the robots exhibit Byzantine failures, starting from the original theorems by Bouzid et al.. Thanks to our formalization, the corresponding COQ developments are quite compact. To our knowledge, these are the first certified (in the sense of formally proved) impossibility results for robot networks

The European Policy for Food Quality and the Fischlers Reform

Fischlers Reform of the Cap has introduced economic support to reinforce the range of instruments aimed at promoting food quality. Before the Reform, European Union market intervention for food quality was confined to the regulatory ground. The paper discusses the economic justifications for financial aid in the case of quality improvement and in the case of information circulation and provision of assurance to consumers. The possibility to add new Quality Schemes at the existing ones is criticized because of the information overcrowding. Furthermore, it is argued that a race to the bottom mechanism could be enforced as a result of the introduction of the possibility to settle Quality Schemes on a national basis. The paper also shows that the unsatisfactory functioning of existing Quality Schemes could be better faced by simplification of the whole quality certification system; by a communication effort at a general level and not only for single Quality Schemes; and by a better coordination of the different strategies of the different stakeholders in the food chains.Quality Schemes, Cap Reform, Information, Reputation, Economic Support, Agricultural and Food Policy, Food Consumption/Nutrition/Food Safety,

Parameterized Verification of Algorithms for Oblivious Robots on a Ring

We study verification problems for autonomous swarms of mobile robots that self-organize and cooperate to solve global objectives. In particular, we focus in this paper on the model proposed by Suzuki and Yamashita of anonymous robots evolving in a discrete space with a finite number of locations (here, a ring). A large number of algorithms have been proposed working for rings whose size is not a priori fixed and can be hence considered as a parameter. Handmade correctness proofs of these algorithms have been shown to be error-prone, and recent attention had been given to the application of formal methods to automatically prove those. Our work is the first to study the verification problem of such algorithms in the parameter-ized case. We show that safety and reachability problems are undecidable for robots evolving asynchronously. On the positive side, we show that safety properties are decidable in the synchronous case, as well as in the asynchronous case for a particular class of algorithms. Several properties on the protocol can be decided as well. Decision procedures rely on an encoding in Presburger arithmetics formulae that can be verified by an SMT-solver. Feasibility of our approach is demonstrated by the encoding of several case studies

Combatting electoral traces: the Dutch tempest discussion and beyond

In the Dutch e-voting debate, the crucial issue leading to the abandonment of all electronic voting machines was compromising radiation, or tempest. Other countries, however, do not seem to be bothered by this risk. In this paper, we use actor-network theory to analyse the socio-technical origins of the Dutch tempest issue in e-voting, and its consequences for e-voting beyond the Netherlands. We introduce the term electoral traces to denote any physical, digital or social evidence of a voter's choices in an election. From this perspective, we provide guidelines for risk analysis as well as an overview of countermeasures

Virtual Organizations: Two Choice Problems

This paper reviews some virtual organizations and the costs and benefits of being in a virtual organization. Particular emphasis is given to those costs and benefits deriving from the information technology and processes required to facilitate communication and transaction processing in virtual organizations. Using analytic models, this paper analyzes two problems faced by companies joining virtual organizations and by virtual organizations: • Under what circumstances should a firm join a virtual organization and when should they do extensive information search regarding joining that virtual organization? • Is it possible to chose a set of standards that are optimal for each company and the virtual organization? Arrow’s impossibility theorem is used to find that there is no standard that meets the optimal needs of the virtual organization and each individual company in the virtual organization

Il rapporto tra impresa e agenzia di rating: la soluzione del multi-rating

The credit rating market is characterized by low competition and a potential conflict of interest, due to the system of remuneration of the rating services, which impairs the reliability of the judgement delivered. Multiple credit rating means further costs for companies, because of the fees paid to more than one rating agency, but it does bring significant benefits in terms of the dissemination, on the market, of judgements concerning the companies. This paper examines the relationship between the number of rating announcements concerning a company and the performance of the securities issued by that company, besides the effects of discordant ratings assigned to a company by different rating agencies (so-called “split rating”), and presents a detailed study of multiple credit rating and of the advantages determined by the placement of issued securities at higher prices, in connection with the new ratings assigned by different agencies. An analysis of split-rating completes this overview of the issue, highlighting how the weight carried by the different rating agencies can affect market reactions.Multi-rating; split-rating and rating agencies