Un environnement formel d'assistance à la modélisation de protocoles

The use of protocol design toolkits based on UML profiles has been hampered by the lack of methodological support. Indeed, those toolkits should include an assistant based on patterns and dedicated to driving the designer step by step through a well defined methodology. Thus, the TURTLE UML profile is extended with widely accepted service and protocol-oriented patterns. These patterns are built upon UML analysis diagrams i.e. use case, interaction overview and sequence diagrams. Moreover, all these patterns and diagrams have a formal semantics. Finally, they have been implemented in TTool, the open-source toolkit supporting TURTLE. The proposed approach remains general and may be applied to various modeling languages and use-case analysis driven processes

Pattern formation driven by cross--diffusion in a 2D domain

In this work we investigate the process of pattern formation in a two dimensional domain for a reaction-diffusion system with nonlinear diffusion terms and the competitive Lotka-Volterra kinetics. The linear stability analysis shows that cross-diffusion, through Turing bifurcation, is the key mechanism for the formation of spatial patterns. We show that the bifurcation can be regular, degenerate non-resonant and resonant. We use multiple scales expansions to derive the amplitude equations appropriate for each case and show that the system supports patterns like rolls, squares, mixed-mode patterns, supersquares, hexagonal patterns

Proof of Razumov-Stroganov conjecture for some infinite families of link patterns

We prove the Razumov--Stroganov conjecture relating ground state of the O(1) loop model and counting of Fully Packed Loops in the case of certain types of link patterns. The main focus is on link patterns with three series of nested arches, for which we use as key ingredient of the proof a generalization of the Mac Mahon formula for the number of plane partitions which includes three series of parameters

Interferometry of hyper-Rayleigh scattering by inhomogeneous thin films

The use of specific symmetry properties of the optical second-harmonic generation (the s,s-exclusion rule) has allowed us to observe high-contrast hyper-Rayleigh interference patterns in a completely diffuse light - an effect having no analog in case of linear (Rayleigh) scattering.Comment: 8 pages, 3 figure

Curriki: Facilitating Use and User Engagement Around Open Educational Resources

Through interviews with the Curriki management team, analysis of internal documents,observations of internal user data collection practices, and a survey and interviews with Curriki users, the Curriki case study explored use patterns and user perceptions of the site, its resources and tools. The specific questions addressed include: 1) how often and why users are coming to Curriki; 2) how they use and engage around the Curriki site, its tools and its resources; and 3) what factors help or hinder engagement and use. The goal of this case study has been to develop an understanding of the mechanisms and processes that can help to attract and sustain users over time, and to facilitate and enhance their use, reuse and content contribution experiences

The Dynamics of a Genetic Algorithm for a Simple Learning Problem

A formalism for describing the dynamics of Genetic Algorithms (GAs) using methods from statistical mechanics is applied to the problem of generalization in a perceptron with binary weights. The dynamics are solved for the case where a new batch of training patterns is presented to each population member each generation, which considerably simplifies the calculation. The theory is shown to agree closely to simulations of a real GA averaged over many runs, accurately predicting the mean best solution found. For weak selection and large problem size the difference equations describing the dynamics can be expressed analytically and we find that the effects of noise due to the finite size of each training batch can be removed by increasing the population size appropriately. If this population resizing is used, one can deduce the most computationally efficient size of training batch each generation. For independent patterns this choice also gives the minimum total number of training patterns used. Although using independent patterns is a very inefficient use of training patterns in general, this work may also prove useful for determining the optimum batch size in the case where patterns are recycled.Comment: 28 pages, 4 Postscript figures. Latex using IOP macros ioplppt and iopl12 which are included. To appear in Journal of Physics A. Also available at ftp://ftp.cs.man.ac.uk/pub/ai/jls/GAlearn.ps.gz and http://www.cs.man.ac.uk/~jl

Towards security monitoring patterns

Runtime monitoring is performed during system execution to detect whether the system’s behaviour deviates from that described by requirements. To support this activity we have developed a monitoring framework that expresses the requirements to be monitored in event calculus – a formal temporal first order language. Following an investigation of how this framework could be used to monitor security requirements, in this paper we propose patterns for expressing three basic types of such requirements, namely confidentiality, integrity and availability. These patterns aim to ease the task of specifying confidentiality, integrity and availability requirements in monitorable forms by non-expert users. The paper illustrates the use of these patterns using examples of an industrial case study