On the Hardness of the Strongly Dependent Decision Problem

We present necessary and sufficient conditions for solving the strongly dependent decision (SDD) problem in various distributed systems. Our main contribution is a novel characterization of the SDD problem based on point-set topology. For partially synchronous systems, we show that any algorithm that solves the SDD problem induces a set of executions that is closed with respect to the point-set topology. We also show that the SDD problem is not solvable in the asynchronous system augmented with any arbitrarily strong failure detectors.Comment: Appeared in ICDCN 201

Solving k-Set Agreement with Stable Skeleton Graphs

In this paper we consider the k-set agreement problem in distributed message-passing systems using a round-based approach: Both synchrony of communication and failures are captured just by means of the messages that arrive within a round, resulting in round-by-round communication graphs that can be characterized by simple communication predicates. We introduce the weak communication predicate PSources(k) and show that it is tight for k-set agreement, in the following sense: We (i) prove that there is no algorithm for solving (k-1)-set agreement in systems characterized by PSources(k), and (ii) present a novel distributed algorithm that achieves k-set agreement in runs where PSources(k) holds. Our algorithm uses local approximations of the stable skeleton graph, which reflects the underlying perpetual synchrony of a run. We prove that this approximation is correct in all runs, regardless of the communication predicate, and show that graph-theoretic properties of the stable skeleton graph can be used to solve k-set agreement if PSources(k) holds.Comment: to appear in 16th IEEE Workshop on Dependable Parallel, Distributed and Network-Centric System

Socio-economical dynamics as a solvable spin system on co-evolving networks

We consider social systems in which agents are not only characterized by their states but also have the freedom to choose their interaction partners to maximize their utility. We map such systems onto an Ising model in which spins are dynamically coupled by links in a dynamical network. In this model there are two dynamical quantities which arrange towards a minimum energy state in the canonical framework: the spins, s_i, and the adjacency matrix elements, c_{ij}. The model is exactly solvable because microcanonical partition functions reduce to products of binomial factors as a direct consequence of the c_{ij} minimizing energy. We solve the system for finite sizes and for the two possible thermodynamic limits and discuss the phase diagrams.Comment: 5 pages 3 fig

Fast Consensus under Eventually Stabilizing Message Adversaries

This paper is devoted to deterministic consensus in synchronous dynamic networks with unidirectional links, which are under the control of an omniscient message adversary. Motivated by unpredictable node/system initialization times and long-lasting periods of massive transient faults, we consider message adversaries that guarantee periods of less erratic message loss only eventually: We present a tight bound of $2D+1$ for the termination time of consensus under a message adversary that eventually guarantees a single vertex-stable root component with dynamic network diameter $D$, as well as a simple algorithm that matches this bound. It effectively halves the termination time $4D+1$ achieved by an existing consensus algorithm, which also works under our message adversary. We also introduce a generalized, considerably stronger variant of our message adversary, and show that our new algorithm, unlike the existing one, still works correctly under it.Comment: 13 pages, 5 figures, updated reference

The Ethics of Cookies: Exploring the Collection of Big Data and Its Ramifications

Technology is taking over the world. In every aspect of human life, technology has been able to provide some sort of help or solution. At the forefront of this revolution is the Internet and with it, the activity of day-to-day life that now takes place online. This rapid takeover pushes technological innovations to develop quickly, pushing boundaries and creating a new way of life. Today in the United States, websites are allowed to track user data. When a user clicks on a website that intends on documenting the user\u27s actions, the website installs a tracker, otherwise known as cookie. Websites then use this collected data to create a profile for each and every user that visits their site. This process creates a vast database that has changed the methods of online marketing and increased business revenue. Although websites in the United States are now starting to alert users of cookie collecting, due to the implementation of the European Union\u27s recent General Data Protection Regulation, the alerts are full of lengthy legal jargon, which means that users don\u27t understand what is happening to their data when they browse a website. The four pillars of ethics, when applied to online data collection, suggest that there are issues with autonomy, nonmaleficence, beneficence, and justice within this data collection field. Due to the fast-paced development of technology, there has not been enough time for regulation to catch up with the major companies that are paving the way for big data practices. Along with the pillars of ethics, privacy and security are at stake, not just for the individual consumer, but for society as a whole

Sex on TV 2

Part of a series that examines the nature and extent of sexual messages conveyed on TV. Tracks changes that occur over time in the treatment of sexual topics, including references to possible risks or responsibilities. Based on a 1999-2000 program sample

Sex on TV 3

Part of a series that examines the nature and extent of sexual messages conveyed on TV. Tracks changes that occur over time in the treatment of sexual topics, including references to possible risks or responsibilities. Based on a 2001-2002 program sampl

Sex on TV: Content and Context

Part of a series that examines the nature and extent of sexual messages conveyed on American television. Focuses on references to contraception, safer sex, and waiting to have sex. Based on a sample of 1997-1998 programs