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Search Results: 1 - 10 of 7515 matches for " Claudio Bezzi "
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Evaluational Brainstorming  [PDF]
Claudio Bezzi
Sociology Mind (SM) , 2011, DOI: 10.4236/sm.2011.14019
Abstract: Among the evaluation techniques based upon group queries (e.g. focus group), brainstorming does not enjoy particular consideration. This might be the result of its origin and development within organizational and managerial domains, traditionally focused more on “idea production” (and problem solving) than on idea analysis within the context of evaluational and social research. This paper presents a development of classical brainstorming, which is quite useful to evaluation, where the traditional idea-producing step is followed by group analysis and exploration of the shared evaluand-specific semantic space. This evaluational brainstorming is the result of a shared understanding of the evaluand by different stakeholders, who can now ascertain their goals and draw cognitive maps to guide subsequent methodological choices and data gathering requirements.
Machine-Readable Privacy Certificates for Services
Marco Anisetti,Claudio A. Ardagna,Michele Bezzi,Ernesto Damiani,Antonino Sabetta
Computer Science , 2013, DOI: 10.1007/978-3-642-41030-7_31
Abstract: Privacy-aware processing of personal data on the web of services requires managing a number of issues arising both from the technical and the legal domain. Several approaches have been proposed to matching privacy requirements (on the clients side) and privacy guarantees (on the service provider side). Still, the assurance of effective data protection (when possible) relies on substantial human effort and exposes organizations to significant (non-)compliance risks. In this paper we put forward the idea that a privacy certification scheme producing and managing machine-readable artifacts in the form of privacy certificates can play an important role towards the solution of this problem. Digital privacy certificates represent the reasons why a privacy property holds for a service and describe the privacy measures supporting it. Also, privacy certificates can be used to automatically select services whose certificates match the client policies (privacy requirements). Our proposal relies on an evolution of the conceptual model developed in the Assert4Soa project and on a certificate format specifically tailored to represent privacy properties. To validate our approach, we present a worked-out instance showing how privacy property Retention-based unlinkability can be certified for a banking financial service.
An information theoretic approach for privacy metrics
Michele Bezzi
Transactions on Data Privacy , 2010,
Abstract: Organizations often need to release microdata without revealing sensitive information. To this scope, data are anonymized and, to assess the quality of the process, various privacy metrics have been proposed, such as k-anonymity, l-diversity, and t-closeness. These metrics are able to capture different aspects of the disclosure risk, imposing minimal requirements on the association of an individual with the sensitive attributes. If we want to combine them in a optimization problem, we need a common framework able to express all these privacy conditions. Previous studies proposed the notion of mutual information to measure the different kinds of disclosure risks and the utility, but, since mutual information is an average quantity, it is not able to completely express these conditions on single records. We introduce here the notion of one-symbol information (i.e., the contribution to mutual information by a single record) that allows to express and compare the disclosure risk metrics. In addition, we obtain a relation between the risk values t and l, which can be used for parameter setting. We also show, by numerical experiments, how l-diversity and t-closeness can be represented in terms of two different, but equally acceptable, conditions on the information gain..
Quantifying the information transmitted in a single stimulus
Michele Bezzi
Quantitative Biology , 2006,
Abstract: Shannon mutual information provides a measure of how much information is, on average, contained in a set of neural activities about a set of stimuli. It has been extensively used to study neural coding in different brain areas. To apply a similar approach to investigate single stimulus encoding, we need to introduce a quantity specific for a single stimulus. This quantity has been defined in literature by four different measures, but none of them satisfies the same intuitive properties (non-negativity, additivity), that characterize mutual information. We present here a detailed analysis of the different meanings and properties of these four definitions. We show that all these measures satisfy, at least, a weaker additivity condition, i.e. limited to the response set. This allows us to use them for analysing correlated coding, as we illustrate in a toy-example from hippocampal place cells.
Species Formation in Simple Ecosystems
Franco Bagnoli,Michele Bezzi
Physics , 1998, DOI: 10.1142/S0129183198000467
Abstract: In this paper we consider a microscopic model of a simple ecosystem. The basic ingredients of this model are individuals, and both the phenotypic and genotypic levels are taken in account. The model is based on a long range cellular automaton (CA); introducing simple interactions between the individuals, we get some of the complex collective behaviors observed in a real ecosystem. Since our fitness function is smooth, the model does not exhibit the error threshold transition; on the other hand the size of total population is not kept constant, and the mutational meltdown transition is present. We study the effects of competition between genetically similar individuals and how it can lead to species formation. This speciation transition does not depend on the mutation rate. We present also an analytical approximation of the model.
Eigen's Error Threshold and Mutational Meltdown in a Quasispecies Model
F. Bagnoli,M. Bezzi
Physics , 1998, DOI: 10.1142/S0129183198000935
Abstract: We introduce a toy model for interacting populations connected by mutations and limited by a shared resource. We study the presence of Eigen's error threshold and mutational meltdown. The phase diagram of the system shows that the extinction of the whole population due to mutational meltdown can occur well before an eventual error threshold transition.
Competition in a Fitness Landscape
Franco Bagnoli,Michele Bezzi
Physics , 1997,
Abstract: We present an extension of Eigen's model for quasi-species including the competition among individuals, proposed as the simplest mechanism for the formation of new species in a smooth fitness landscape. We are able to obtain analytically the critical threshold for species formation. The comparison with numerical simulations is very good.
Speciation as Pattern Formation by Competition in a Smooth Fitness Landscape
Franco Bagnoli,Michele Bezzi
Physics , 1997, DOI: 10.1103/PhysRevLett.79.3302
Abstract: We investigate the problem of speciation and coexistence in simple ecosystems when the competition among individuals is included in the Eigen model for quasi-species. By suggesting an analogy between the competition among strains and the diffusion of a chemical inhibitor in a reaction-diffusion system, the speciation phenomenon is considered the analogous of chemical pattern formation in genetic space. In the limit of vanishing mutation rate we obtain analytically the conditions for speciation. Using different forms of the competition interaction we show that the speciation is absent for the genetic equivalent of a normal diffusing inhibitor, and is present for shorter-range interactions. The comparison with numerical simulations is very good.
Phase Disorder Effects in a Cellular Automaton Model of Epidemic Propagation
M. Bezzi,R. Livi
Physics , 1998,
Abstract: A deterministic cellular automaton rule defined on the Moore neighbourhood is studied as a model of epidemic propagation. The directed nature of the interaction between cells allows one to introduce the dependence on a disorder parameter that determines the fraction of ``in-phase'' cells. Phase-disorder is shown to produce peculiar changes in the dynamical and statistical properties of the different evolution regimes obtained by varying the infection and the immunization periods. In particular, the finite-velocity spreading of perturbations, characterizing chaotic evolution, can be prevented by localization effects induced by phase-disorder, that may also yield spatial isotropy of the infection propagation as a statistical effect. Analogously, the structure of phase-synchronous ordered patterns is rapidly lost as soon as phase-disorder is increased, yielding a defect-mediated turbulent regime.
Towards understanding and modelling office daily life
Michele Bezzi,Robin Groenevelt
Computer Science , 2007,
Abstract: Measuring and modeling human behavior is a very complex task. In this paper we present our initial thoughts on modeling and automatic recognition of some human activities in an office. We argue that to successfully model human activities, we need to consider both individual behavior and group dynamics. To demonstrate these theoretical approaches, we introduce an experimental system for analyzing everyday activity in our office.
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