Directrius per a l'accessibilitat al contingut web, versió 1.0

Aquestes directrius expliquen com fer que el contingut web sigui accessible a persones amb discapacitats i s'adrecen a creadors de contingut (autors de pàgines web o dissenyadors de llocs web) i a creadors d'eines d'autor. L'objectiu principal d'aquestes directrius és promoure l'accessibilitat. Tanmateix, l'aplicació de les directrius facilitarà l'accés al contingut a tot tipus d'usuari, sigui quin sigui l'agent d'usuari usat (navegador web, navegador de veu, telèfon mòbil, ordinador de cotxe, etc.) o les condicions de l'entorn de consulta (entorns sorollosos, espais mal il·luminats, entorns en què no es poden usar les mans, etc.). L'aplicació d'aquestes directrius també ajudarà els usuaris a trobar la informació d'una manera més ràpida dins el web. Les directrius no pretenen desincentivar l'ús d'imatges, vídeo, etc., sinó que expliquen com fer que el contingut multimèdia sigui més accessible a una àmplia audiència.Aquest és un document de referència per a uns principis d'accessibilitat i idees de disseny. Algunes de les estratègies comentades tracten d'aspectes relatius a la internacionalització del web i a l'accés des de terminals mòbils. Tanmateix, el document se centra en l'accessibilitat i no tracta exhaustivament dels aspectes relacionats amb altres activitats del W3C. Si voleu més informació sobre aquests temes podeu consultar les pàgines inicials W3C Mobile Access Activity (per a l'accés des de terminals mòbils) i W3C Internationalization Activity (per als aspectes d'internacionalització).Aquest document està pensat per a ser estable en el temps i, per tant, no dóna informació específica sobre si els navegadors funcionen o no amb una determinada tecnologia, ja que aquesta informació varia molt ràpidament. Aquesta informació es pot trobar al web de la Web Accessibility Initiative ,WAI, (Iniciativa d'Accessibilitat Web) [WAI-UA-SUPPORT].Aquest document inclou un annex que organitza tots els punts de verificació ordenats per tema i per prioritat. Els punts de l'annex estan enllaçats a les respectives definicions en el document. Els temes recollits en l'annex inclouen les imatges, el contingut multimèdia, les taules, els marcs, els formularis i els scripts. L'annex es presenta en forma de taula o com a simple llista.Un document a part, amb el títol Techniques for Web Content Accessibility Guidelines 1.0 (Tècniques per a les directrius per a l'accessibilitat al contingut web, versió 1.0) ([TECHNIQUES]) explica com posar a la pràctica els punts citats fins aquí. El document de tècniques explica cada punt amb més detalls i dóna exemples usant el llenguatge d'etiquetatge d'hipertext (HTML), fulls d'estil en cascada (CSS), el llenguatge d'integració multimèdia sincronitzada (SMIL) o el llenguatge d'etiquetatge matemàtic (MathML). Aquest document també inclou tècniques per a provar o validar una pàgina web i un índex dels elements i atributs HTML amb les tècniques que els usen. El document de tècniques està pensat per a seguir de prop els canvis tecnològics i es preveu que s'actualitzi més sovint que les directrius.Nota: Algunes de les característiques descrites en les directrius no estan encara implementades en tots els navegadors o eines multimèdia; en concret pot ser que no es puguin utilitzar funcions noves d'HTML 4.0, de CSS1 o CSS2.Les Directrius per a l'accessibilitat al contingut web, versió 1.0 són part d'una col·lecció de directrius sobre accessibilitat publicades per la Web Accessibility Initiative, WAI (Iniciativa d'Accessibilitat Web). La col·lecció comprèn User Agent Accessibility Guidelines (Directrius d'accessibilitat per a agents d'usuari) [WAI-USERAGENT] i Authoring Tool Accessibility Guidelines (Directrius d'accessibilitat per a eines d'autor [WAI-AUTOOLS].

Directrius per a l'accessibilitat al contingut web, versió 1.0. Recomanació de W3C, 5 de maig de 1999

Aquestes directrius expliquen com fer que el contingut web sigui accessible a persones ambdiscapacitats i s'adrecen a creadors de contingut (autors de pàgines web o dissenyadors de llocs web) ia creadors d'eines d'autor. L'objectiu principal d'aquestes directrius és promoure l'accessibilitat.Tanmateix, l'aplicació de les directrius facilitarà l'accés al contingut a tot tipus d'usuari, sigui quin siguil'agent d'usuari usat (navegador web, navegador de veu, telèfon mòbil, ordinador de cotxe, etc.) o les condicions de l'entorn de consulta (entorns sorollosos, espais mal il·luminats, entorns en què no es poden usar lesmans, etc.). L'aplicació d'aquestes directrius també ajudarà els usuaris a trobar la informació d'unamanera més ràpida dins el web. Les directrius no pretenen desincentivar l'ús d'imatges, vídeo, etc., sinóque expliquen com fer que el contingut multimèdia sigui més accessible a una àmplia audiència.Aquest és un document de referència per a uns principis d'accessibilitat i idees de disseny. Algunes deles estratègies comentades tracten d'aspectes relatius a la internacionalització del web i a l'accés desde terminals mòbils. Tanmateix, el document se centra en l'accessibilitat i no tracta exhaustivament delsaspectes relacionats amb altres activitats del W3C. Si voleu més informació sobre aquests temes podeuconsultar les pàgines inicials W3C Mobile Access Activity (per a l'accés des de terminals mòbils) i W3CInternationalization Activity (per als aspectes d'internacionalització). Aquest document està pensat per a ser estable en el temps i, per tant, no dóna informació específica sobre si els navegadors funcionen o no amb una determinada tecnologia, ja que aquesta informació varia molt ràpidament. Aquesta informació es pot trobar al web de la Web Accessibility Initiative ,WAI, (Iniciativa d'Accessibilitat Web) [WAI-UA-SUPPORT].Aquest document inclou un annex que organitza tots els punts de verificació ordenats per tema i perprioritat. Els punts de l'annex estan enllaçats a les respectives definicions en el document. Els temesrecollits en l'annex inclouen les imatges, el contingut multimèdia, les taules, els marcs, els formularis iels scripts. L'annex es presenta en forma de taula o com a simple llista. Un document a part, amb el títol Techniques for Web Content Accessibility Guidelines 1.0 (Tècniques per a les directrius per a l'accessibilitat al contingut web, versió 1.0) ([TECHNIQUES]) explica com posar a la pràctica els punts citats fins aquí. El document de tècniques explica cada punt amb més detalls i dóna exemples usant el llenguatge d'etiquetatge d'hipertext (HTML), fulls d'estil en cascada (CSS), el llenguatge d'integració multimèdia sincronitzada (SMIL) o el llenguatge d'etiquetatge matemàtic (MathML). Aquest document també inclou tècniques per a provar o validar una pàgina web i un índex Directrius per a l'accessibilitat al contingut web, versió 1.0 dels elements i atributs HTML amb les tècniques que els usen. El document de tècniques està pensat per a seguir de prop els canvis tecnològics i es preveu que s'actualitzi més sovint que les directrius.

On-line event detection by recursive dynamic principal component analysis and gas sensor arrays under drift conditions

Leakage detection is an important issue in many chemical sensing applications. Leakage detection hy thresholds suffers from important drawbacks when sensors have serious drifts or they are affected by cross-sensitivities. Here we present an adaptive method based in a Dynamic Principal Component Analysis that models the relationships between the sensors in the may. In normal conditions a certain variance distribution characterizes sensor signals. However, in the presence of a new source of variance the PCA decomposition changes drastically. In order to prevent the influence of sensor drifts the model is adaptive and it is calculated in a recursive manner with minimum computational effort. The behavior of this technique is studied with synthetic signals and with real signals arising by oil vapor leakages in an air compressor. Results clearly demonstrate the efficiency of the proposed method.

Drift compensation of gas sensor array data by common principal component analysis

A new drift compensation method based on Common Principal Component Analysis (CPCA) is proposed. The drift variance in data is found as the principal components computed by CPCA. This method finds components that are common for all gasses in feature space. The method is compared in classification task with respect to the other approaches published where the drift direction is estimated through a Principal Component Analysis (PCA) of a reference gas. The proposed new method ¿ employing no specific reference gas, but information from all gases ¿has shown the same performance as the traditional approach with the best-fitted reference gas. Results are shown with data lasting 7-months including three gases at different concentrations for an array of 17 polymeric sensors.

Organisational adaptation of multi-agent systems in a peer-to-peer scenario

Organisations in Multi-Agent Systems (MAS) have proven to be successful in regulating agent societies. Nevertheless, changes in agents' behaviour or in the dynamics of the environment may lead to a poor fulfilment of the system's purposes, and so the entire organisation needs to be adapted. In this paper we focus on endowing the organisation with adaptation capabilities, instead of expecting agents to be capable of adapting the organisation by themselves. We regard this organisational adaptation as an assisting service provided by what we call the Assistance Layer. Our generic Two Level Assisted MAS Architecture (2-LAMA) incorporates such a layer. We empirically evaluate this approach by means of an agent-based simulator we have developed for the P2P sharing network domain. This simulator implements 2-LAMA architecture and supports the comparison between different adaptation methods, as well as, with the standard BitTorrent protocol. In particular, we present two alternatives to perform norm adaptation and one method to adapt agents'relationships. The results show improved performance and demonstrate that the cost of introducing an additional layer in charge of the system's adaptation is lower than its benefits.

Retaining principal components for discrete variables

The present study discusses retention criteria for principal components analysis (PCA) applied to Likert scale items typical in psychological questionnaires. The main aim is to recommend applied researchers to restrain from relying only on the eigenvalue-than-one criterion; alternative procedures are suggested for adjusting for sampling error. An additional objective is to add evidence on the consequences of applying this rule when PCA is used with discrete variables. The experimental conditions were studied by means of Monte Carlo sampling including several sample sizes, different number of variables and answer alternatives, and four non-normal distributions. The results suggest that even when all the items and thus the underlying dimensions are independent, eigenvalues greater than one are frequent and they can explain up to 80% of the variance in data, meeting the empirical criterion. The consequences of using Kaiser"s rule are illustrated with a clinical psychology example. The size of the eigenvalues resulted to be a function of the sample size and the number of variables, which is also the case for parallel analysis as previous research shows. To enhance the application of alternative criteria, an R package was developed for deciding the number of principal components to retain by means of confidence intervals constructed about the eigenvalues corresponding to lack of relationship between discrete variables.

Spatial behavior in groups: an agent-based approach

We present an agent-based model with the aim of studying how macro-level dynamics of spatial distances among interacting individuals in a closed space emerge from micro-level dyadic and local interactions. Our agents moved on a lattice (referred to as a room) using a model implemented in a computer program called P-Space in order to minimize their dissatisfaction, defined as a function of the discrepancy between the real distance and the ideal, or desired, distance between agents. Ideal distances evolved in accordance with the agent's personal and social space, which changed throughout the dynamics of the interactions among the agents. In the first set of simulations we studied the effects of the parameters of the function that generated ideal distances, and in a second set we explored how group macrolevel behavior depended on model parameters and other variables. We learned that certain parameter values yielded consistent patterns in the agents' personal and social spaces, which in turn led to avoidance and approaching behaviors in the agents. We also found that the spatial behavior of the group of agents as a whole was influenced by the values of the model parameters, as well as by other variables such as the number of agents. Our work demonstrates that the bottom-up approach is a useful way of explaining macro-level spatial behavior. The proposed model is also shown to be a powerful tool for simulating the spatial behavior of groups of interacting individuals.

Diagnosing Patients Combining Principal Components Analysis and Case Based Reasoning

This paper addresses the application of a PCA analysis on categorical data prior to diagnose a patients data set using a Case-Based Reasoning (CBR) system. The particularity is that the standard PCA techniques are designed to deal with numerical attributes, but our medical data set contains many categorical data and alternative methods as RS-PCA are required. Thus, we propose to hybridize RS-PCA (Regular Simplex PCA) and a simple CBR. Results show how the hybrid system produces similar results when diagnosing a medical data set, that the ones obtained when using the original attributes. These results are quite promising since they allow to diagnose with less computation effort and memory storage

Promoting the development of secure mobile agent applications

Peer-reviewed

Securing dynamic itineraries for mobile agent applications

In this paper we present a novel mechanism for the protection of dynamic itineraries for mobile agent applications. Itineraries that are decided as the agent goes are essential in complex applications based on mobile agents, but no approach has been presented until now to protect them. We have conceived a cryptographic scheme for shielding dynamic itineraries from tampering, impersonation and disclosure. By using trust strategically, our scheme provides a balanced trade-off between flexibility and security. Our protection scheme has been thought always bearing in mind a feasible implementation, and thus facilitates the development of applications that make use of it. An example application based on a real healthcare scenario is also presented to show its operation.

Moral Hazard in Repeated Procurement of Services

This paper analyzes repeated procurement of services as a four-stage game divided into two periods. In each period there is (1) a contest stage à la Tullock in which the principal selects an agent and (2) a service stage in which the selected agent provides a service. Since this service effort is non-verifiable, the principal faces a moral hazard problem at the service stages. This work considers how the principal should design the period-two contest to mitigate the moral hazard problem in the period-one service stage and to maximize total service and contest efforts. It is shown that the principal must take account of the agent's past service effort in the period-two contest success function. The results indicate that the optimal way to introduce this `bias' is to choose a certain degree of complementarity between past service and current contest efforts. This result shows that contests with `additive bias' (`multiplicative bias') are optimal in incentive problems when effort cost is low (high). Furthermore, it is shown that the severity of the moral hazard problem increases with the cost of service effort (compared to the cost of contest effort) and the number of agents. Finally, the results are extended to more general contest success functions. JEL classification: C72; D82 Key words: Biased contests; Moral Hazard; Repeated Game; Incentives.

Seroprevalence of Angiostrongylus cantonensis in wild rodents from the Canary Islands

Background: Angiostrongylus cantonensis is a lungworm of rats (Muridae) that is the causative agent of human cerebral angiostrongyliasis. The life cycle of A. cantonensis involves rats and mollusks as the definitive and intermediate hosts, respectively. This study was designed to increase the knowledge about the occurrence and distribution of A. cantonensis in its definitive host in the Canary Islands, using parasitological and serological analysis in different areas and age groups.Methodology/Principal Findings: Between 2009 and 2010, 54 black rats (Rattus rattus) from Tenerife were captured from six human-inhabited areas and sera samples were obtained. The lung nematodes were identified by morphological and molecular tools as A. cantonensis. The 31-kDa glycoprotein antigen was purified from A. cantonensis adult worms by electrophoresis and electroelution. Of the 54 tested rodents, 30 showed IgG antibodies against A. cantonensis 31-kDa antigen by ELISA. Therefore, the overall seroprevalence was 55.6% (95% CI: 42.4-68). Seroprevalent rodents were found in all the 6 areas. This 31-kDa antigen was not recognized by some sera of rats infected by other helminth species (but not A. cantonensis). Seroprevalence of IgG antibodies against A. cantonensis and prevalence based on the presence of adult worms showed significant correlation (R2 = 0.954, p,0.05). Conclusions/Significance: The present results could indicate a high prevalence of A. cantonensisin Tenerife and suggest the inclusion of two new zones in the distribution area of the parasite. The commonness and wide distribution of A. cantonensis in rats implies the presence of intermediate hosts, indicating that humans may be at risk of getting infected.

ACACIA: an agent-based program for simulating behavior to reach long-term goals

We present ACACIA, an agent-based program implemented in Java StarLogo 2.0 that simulates a two-dimensional microworld populated by agents, obstacles and goals. Our program simulates how agents can reach long-term goals by following sensorial-motor couplings (SMCs) that control how the agents interact with their environment and other agents through a process of local categorization. Thus, while acting in accordance with this set of SMCs, the agents reach their goals through the emergence of global behaviors. This agent-based simulation program would allow us to understand some psychological processes such as planning behavior from the point of view that the complexity of these processes is the result of agent-environment interaction.

Flocking behaviour: Agent-based simulation and hierarchical leadership.

We have studied how leaders emerge in a group as a consequence of interactions among its members. We propose that leaders can emerge as a consequence of a self-organized process based on local rules of dyadic interactions among individuals. Flocks are an example of self-organized behaviour in a group and properties similar to those observed in flocks might also explain some of the dynamics and organization of human groups. We developed an agent-based model that generated flocks in a virtual world and implemented it in a multi-agent simulation computer program that computed indices at each time step of the simulation to quantify the degree to which a group moved in a coordinated way (index of flocking behaviour) and the degree to which specific individuals led the group (index of hierarchical leadership). We ran several series of simulations in order to test our model and determine how these indices behaved under specific agent and world conditions. We identified the agent, world property, and model parameters that made stable, compact flocks emerge, and explored possible environmental properties that predicted the probability of becoming a leader.

Emergent patterns of social organization in captive Cercocebus torquatus: Testing the GrooFiWorld agent-based model

We empirically applied the GrooFiWorld agent-based model (Puga-González et al. 2009) in a group of captive mangabeys (Cercocebus torquatus). We analysed several measurements related to aggression and affiliative patterns. The group adopted a combination of despotic and egalitarian behaviours resulting from the behavioural flexibility observed in the Cercopithecinae subfamily. Our study also demonstrates that the GrooFiWorld agent-based model can be extended to other members of the Cercopithecinae subfamily generating parsimonious hypotheses related to the social organization.