Recent events have illustrated the Internet’s vulnerability to both denial of service (DoS) attacks and flash crowds in which links (or servers) in the network become severely congested. In both DoS attacks and flash crowds, the congestion is neither due to a single flow, nor due to a general increase in traffic, but to a well-defined subset of the traffic — an aggregate. This paper proposes ag...

Recent events have highlighted the importance of good models of crowds, however many existing crowd models are either computationally inefficient, or are missing a crucial human behaviour in crowds: local pushing. After discussing some essential aspects of force in crowds, and considering some existing models, we propose an efficient agent-based model of crowd evacuation that incorporates pushi...

Whereas crowdsourcing as a topic has often been addressed in recent literature, web-based crowdworking platforms that manage the interface between crowdsourcers and crowdworkers have not received much attention so far. Furthermore, most of these platforms focus on either the management of external or internal crowds; platforms that handle both groups are rare. This paper investigates such a pro...

Although researchers have documented many instances of crowd wisdom, it is important to know whether some kinds of judgments may lead the crowd astray, whether crowds’ judgments improve with feedback over time, and whether crowds’ judgments can be improved by changing the way judgments are elicited. We investigated these questions in a sports gambling context (predictions against point spreads)...

Ever since Galton's classic demonstration of the wisdom of crowds in estimating the weight of a slaughtered ox, scholars of the mind and the public alike have been fascinated by the counterintuitive accuracy achieved by simply averaging a number of people's estimates. Surprisingly, individuals can, to some extent, harness the wisdom of crowds within the confines of their own mind by averaging s...

The aim of this chapter is to introduce the current researches focused on the modeling and simulation of crowds of pedestrians. Research efforts on this topic are aimed, on one hand, at improving the scientific investigation of crowd related phenomena and, on the other, at the exploitation of the developed models and simulators to support designers and decision makers in their activities by pro...

A conventional Content Distribution Network (CDN) has a static structure, therefore, it is not an effective solution to a flash crowd, that is a rapid increase in server load caused by a sudden access concentration. We have proposed an adaptive CDN, FCAN (Flash Crowds Alleviation Network), which changes its structure dynamically against flash crowds. In this paper, we verify FCAN on a real worl...

I describe an algorithm for simulating crowds in a variety of situations. I formalize the problem as a Markov Decision Process and then apply randomization techniques, along with physically and biologically based methods in order to feasibly solve this problem without discretization. I then evaluate my model with that of simple Boids flocking behavior in order to determine how successful the mo...

The recent spread of communicable diseases like swine flu, disasters like stampedes and ongoing security issues have made management of large crowded events more critical than ever before. Managing large crowds is a very complex, challenging and costly exercise. Many of the problems encountered in crowd management can be minimized by the use of RFID and other wireless technologies. These techno...

Flash crowds can cripple a web site’s performance. Since they are infrequent and unpredictable, these floods do not justify the cost of traditional commercial solutions. We describe Backslash, a collaborative web mirroring system run by a collective of web sites that wish to protect themselves from flash crowds. Backslash is built on a distributed hash table overlay and uses the structure of th...