The Design and Evaluation of a Large-Scale Real-Walking Locomotion Interface

Redirected Free Exploration with Distractors (RFED) is a large-scale real-walking locomotion interface developed to enable people to walk freely in virtual environments that are larger than the tracked space in their facility. This paper describes the RFED system in detail and reports on a user study that evaluated RFED by comparing it to walking-in-place and joystick interfaces. The RFED system is composed of two major components, redirection and distractors. This paper discusses design challenges, implementation details, and lessons learned during the development of two working RFED systems. The evaluation study examined the effect of the locomotion interface on users’ cognitive performance on navigation and wayfinding measures. The results suggest that participants using RFED were significantly better at navigating and wayfinding through virtual mazes than participants using walking-in-place and joystick interfaces. Participants traveled shorter distances, made fewer wrong turns, pointed to hidden targets more accurately and more quickly, and were able to place and label targets on maps more accurately, and more accurately estimate the virtual environment size

Perceptual Manipulations for Hiding Image Transformations in Virtual Reality

Users of a virtual reality make frequent gaze shifts and head movements to explore their surrounding environment. Saccades are rapid, ballistic, conjugate eye movements that reposition our gaze, and in doing so create large-field motion on our retina. Due to the high speed motion on the retina during saccades, the brain suppresses the visual signals from the eye, a perceptual phenomenon known as the saccadic suppression. These moments of visual blindness can help hide the display graphical updates in a virtual reality. In this dissertation, I investigated how the visibility of various image transformations differed, during combinations of saccade and head rotation conditions. Additionally, I studied how hand and gaze interaction, affected image change discrimination in an inattentional blindness task. I conducted four psychophysical experiments in desktop or head-mounted VR. In the eye tracking studies, users viewed 3D scenes, and were triggered to make a vertical or horizontal saccade. During the saccade an instantaneous translation or rotation was applied to the virtual camera used to render the scene. Participants were required to indicate the direction of these transitions after each trial. The results showed that type and size of the image transformation affected change detectability. During horizontal or vertical saccades, rotations along the roll axis were the most detectable, while horizontal and vertical translations were least noticed. In a second similar study, I added a constant camera motion to simulate a head rotation, and in a third study, I compared active head rotation with a simulated rotation or a static head. I found less sensitivity to transsaccadic horizontal compared to vertical camera shifts during simulated or real head pan. Conversely, during simulated or real head tilt observers were less sensitive to transsaccadic vertical than horizontal camera shifts. In addition, in my multi-interactive inattentional blindness experiment, I compared sensitivity to sudden image transformations when a participant used their hand and gaze to move and watch an object, to when they only watched it move. The results confirmed that when involved in a primary task that requires focus and attention with two interaction modalities (gaze and hand), a visual stimuli can better be hidden than when only one sense (vision) is involved. Understanding the effect of continuous head movement and attention on the visibility of a sudden transsaccadic change can help optimize the visual performance of gaze-contingent displays and improve user experience. Perceptually suppressed rotations or translations can be used to introduce imperceptible changes in virtual camera pose in applications such as networked gaming, collaborative virtual reality and redirected walking. This dissertation suggests that such transformations can be more effective and more substantial during active or passive head motion. Moreover, inattentional blindness during an attention-demanding task provides additional opportunities for imperceptible updates to a visual display

Perceptual Manipulations for Hiding Image Transformations in Virtual Reality

Users of a virtual reality make frequent gaze shifts and head movements to explore their surrounding environment. Saccades are rapid, ballistic, conjugate eye movements that reposition our gaze, and in doing so create large-field motion on our retina. Due to the high speed motion on the retina during saccades, the brain suppresses the visual signals from the eye, a perceptual phenomenon known as the saccadic suppression. These moments of visual blindness can help hide the display graphical updates in a virtual reality. In this dissertation, I investigated how the visibility of various image transformations differed, during combinations of saccade and head rotation conditions. Additionally, I studied how hand and gaze interaction, affected image change discrimination in an inattentional blindness task. I conducted four psychophysical experiments in desktop or head-mounted VR. In the eye tracking studies, users viewed 3D scenes, and were triggered to make a vertical or horizontal saccade. During the saccade an instantaneous translation or rotation was applied to the virtual camera used to render the scene. Participants were required to indicate the direction of these transitions after each trial. The results showed that type and size of the image transformation affected change detectability. During horizontal or vertical saccades, rotations along the roll axis were the most detectable, while horizontal and vertical translations were least noticed. In a second similar study, I added a constant camera motion to simulate a head rotation, and in a third study, I compared active head rotation with a simulated rotation or a static head. I found less sensitivity to transsaccadic horizontal compared to vertical camera shifts during simulated or real head pan. Conversely, during simulated or real head tilt observers were less sensitive to transsaccadic vertical than horizontal camera shifts. In addition, in my multi-interactive inattentional blindness experiment, I compared sensitivity to sudden image transformations when a participant used their hand and gaze to move and watch an object, to when they only watched it move. The results confirmed that when involved in a primary task that requires focus and attention with two interaction modalities (gaze and hand), a visual stimuli can better be hidden than when only one sense (vision) is involved. Understanding the effect of continuous head movement and attention on the visibility of a sudden transsaccadic change can help optimize the visual performance of gaze-contingent displays and improve user experience. Perceptually suppressed rotations or translations can be used to introduce imperceptible changes in virtual camera pose in applications such as networked gaming, collaborative virtual reality and redirected walking. This dissertation suggests that such transformations can be more effective and more substantial during active or passive head motion. Moreover, inattentional blindness during an attention-demanding task provides additional opportunities for imperceptible updates to a visual display

New Measures for the Study of Distributive Mixing in Continuous Creeping Flows

New mathematical measures are developed for the investigation of fluid-fluid mixing in continuous laminar flows as a function of mechanisms of mixing, namely the eigenvectors of the rate of deformation tensor. Previous theoretical work in this field has shown that interfacial reorientation and chaotic advection produce improved mixing over deterministic mixing. However, these previous approaches have failed to explore the nature of the mechanisms of mixing present in the continuously spatially varying flow fields. Four new measures are presented to relate the deformation of an infinitesimal material element to the eigenvectors of the rate of deformation tensor. These expressions characterize material deformation as a function of the spatial relationship between material and the eigenvectors in a variety of general flows. The application of these measures is shown using CFD simulations for three steady flows, the Couette channel, the diverging channel, and the steady state lid driven cavity. These measures improve the understanding of mixing in the various flow field models and produce new insight into the nature of mixing in continuous flow fields

Devising a Strategic Approach to Increase Faculty’s Competence for Formalized Intercultural Teaching and Learning Opportunities in an International School in Africa

The international school is a unique site where a diverse community of host country nationals and expatriates come together to participate in a transnational learning experience. Within this context, the international school is challenged to deliver a culturally responsive learning program with intercultural learning opportunities to meet the needs of a diverse learning community. In addition, it is perceived that with intercultural competence, an international school graduate can gain competitiveness for post-secondary institution admissions and job market movement in an increasingly globalized economy. This organizational improvement plan problematizes a lack of strategy to improve intercultural teaching and learning at a well-established international school located in Africa. It draws upon theoretical concepts of transformative learning and single loop organizational learning to drive organizational change and incorporates concepts of intercultural competence, global citizenship, culturally responsive pedagogy and professional learning communities to inform change improvement planning. The change plan is generative yet practically executed using both transformational and team leadership approaches and applies 3 ethical paradigm lenses, underpinned by consequentialist philosophy. An integrated, multimethod approach to change implementation, monitoring, evaluation and communication scaffolds the transformation of an adaptive learning culture and an evolved curriculum with improved intercultural teaching and learning opportunities. The outcome of the change plan represents how theory can be translated into practice to impact student learning. The ramifications of improved intercultural teaching and learning is seen to extend beyond the international school site and affect the wider communities that students and faculty frequent

Hybrid multi-objective trajectory optimization of low-thrust space mission design

Mención Internacional en el título de doctorThe overall goal of this dissertation is to develop multi-objective optimization algorithms for computing low-thrust trajectories. The thesis is motivated by the increasing number of space projects that will benefit from low-thrust propulsion technologies to gain unprecedented scientific, economic and social return. The low-cost design of such missions and the inclusion of concurrent engineering practices during the preliminary design phase demand advanced tools to rapidly explore different solutions and to benchmark them with respect to multiple conicting criteria. However, the determination of optimal low-thrust transfers is a challenging task and remains an active research field that seeks performance improvements. This work contributes to increase the efficiency of searching wide design spaces, reduce the amount of necessary human involvement, and enhance the capabilities to include complex operational constraints. To that end, the general low-thrust trajectory optimization problem is stated as a multi-objective Hybrid Optimal Control Problem. This formulation allows to simultaneously optimize discrete decisionmaking processes, discrete dynamics, and the continuous low-thrust steering law. Within this framework, a sequential two-step solution approach is devised for two different scenarios. The first problem considers the optimization of low-thrust multi-gravity assist trajectories. The proposed solution procedure starts by assuming a planar shape-based model for the interplanetary trajectory. A multi-objective heuristic algorithm combined with a gradient-based solver optimize the parameters de_ning the shape of the trajectory, the number and sequence of the gravity assists, the departure and arrival dates, and the launch excess velocity. In the second step, candidate solutions are deemed as initial guesses to solve the Nonlinear Programming Problem resulting from applying a direct collocation transcription scheme. In this step, the sequence of planetary gravity assists is known and provided by the heuristic search, dynamics is three-dimensional, and the steering law is not predefined. Operational constraints to comply with launch asymptote declination limits and fixed reorientation times during the transfer apply. The presented approach is tested on a rendezvous mission to Ceres, on a yby mission to Jupiter, and on a rendezvous mission to Pluto. Pareto-optimal solutions in terms of time of ight and propellant mass consumed (or alternatively delivered mass) are obtained. Results outperform those found in the literature in terms of optimality while showing the effectiveness of the proposed methodology to generate quick performance estimates. The second problem considers the simultaneous optimization of fully electric, fully chemical and combined chemical-electric orbit raising transfers between Earth's orbits is considered. In the first step of the solution approach, the control law of the electric engine is parameterized by a Lyapunov function. A multi-objective heuristic algorithm selects the optimal propulsion system, the transfer type, the low-thrust control history, as well as the number, orientation, and magnitude of the chemical firings. Earth's shadow, oblateness and Van-Allen radiation effects are included. In the second step, candidate solutions are deemed as initial guesses to solve the Nonlinear Programming Problem resulting from applying a direct collocation scheme. Operational constraints to avoid the GEO ring in combination to slew rate limits and slot phasing constraints are included. The proposed approach is applied to two transfer scenarios to GEO orbit. Pareto-optimal solutions trading of propellant mass, time of ight and solar-cell degradation are obtained. It is identified that the application of operational restrictions causes minor penalties in the objective function. Additionally, the analysis highlights the benefits that combined chemical-electric platforms may provide for future GEO satellites.El objetivo principal de esta trabajo es desarrollar algoritmos de optimización multi-objetivo para la obtención de trayectorias espaciales con motores de bajo empuje. La tesis está motivada por el creciente número de misiones que se van a beneficiar del uso de estas tecnologías para conseguir beneficios científicos, económicos y sociales sin precedentes. El diseño de bajo coste de dichas misiones ligado a los principios de ingeniería concurrente requieren herramientas computacionales avanzadas que exploren rápidamente distintas soluciones y las comparen entre sí respecto a varios criterios. Sin embargo, esta tarea permanece como un campo de investigación activo que busca continuamente mejoras de rendimiento durante el proceso. Este trabajo contribuye a aumentar la eficiencia cuando espacio de diseño es amplio, a reducir la participación humana requerida y a mejorar las capacidades para incluir restricciones operacionales complejas. Para este fin, el problema general de optimización de trayectorias de bajo empuje se presenta como un problema híbrido de control óptimo. Esta formulación permite optimizar al mismo tiempo procesos de toma de decisiones, dinámica discreta y la ley de control del motor. Dentro de este marco, se idea un algoritmo secuencial de dos pasos para dos escenarios diferentes. El primer problema considera la optimización de trayectorias de bajo empuje con múltiples y-bys. El proceso de solución propuesto comienza asumiendo un modelo plano y shape-based para la trayectoria interplanetaria. Un algoritmo de optimización heurístico y multi-objetivo combinado con un resolvedor basado en gradiente optimizan los parámetros de la espiral que definen la forma de la trayectoria, el número y la secuencia de las maniobras gravitacionales, las fechas de salida y llegada, y la velocidad de lanzamiento. En el segundo paso, las soluciones candidatas se usan como estimación inicial para resolver el problema de optimización no lineal que resulta de aplicar un método de transcripción directa. En este paso, las secuencia de y-bys es conocida y determinada por el paso anterior, la dinámica es tridimensional, y la ley de control no está prefinida. Además, se pueden aplicar restricciones operacionales relacionadas con las declinación de la asíntota de salida e imponer tiempos de reorientación fijos. Este enfoque es probado en misiones a Ceres, a Júpiter y a Plutón. Se obtienen soluciones óptimas de Pareto en función del tiempo de vuelo y la masa de combustible consumida (o la masa entregada). Los resultados obtenidos mejoran los disponibles en la literatura en términos de optimalidad, a la vez que reflejan la efectividad de la metodología a propuesta para generar estimaciones rápidas. El segundo problema considera la optimización simultanea de transferencias entre órbitas terrestres que usan propulsión eléctrica, química o una combinación de ambas. En el primer paso del método de solución, la ley de control del motor eléctrico se parametriza por una función de Lyapunov. Un algoritmo de optimización heurístico y multi-objetivo selecciona el sistema propulsivo óptimo, el tipo de transferencia, la ley de control del motor de bajo empuje, así como el número, la orientación y la magnitud de los impulsos químicos. Se incluyen los efectos de la sombra y de la no esfericidad de la Tierra, además de la radiación de Van-Allen. En el segundo paso, las soluciones candidatas se usan como estimación inicial para resolver el problema de optimización no lineal que resulta de aplicar un método de transcripción directa. El método de solución propuesto se aplica a dos transferencias a GEO diferentes. Se obtienen soluciones óptimas de Pareto con respecto a la masa de combustible, el tiempo de vuelo y la degradación de las células solares. Se identifican que la aplicación de las restricciones operacionales penaliza mínimamente la función objetivo. Además, los análisis presentados destacan los beneficios que la propulsión química y eléctrica combinada proporcionarían a los satélites en GEO.Programa de Doctorado en Mecánica de Fluidos por la Universidad Carlos III de Madrid; la Universidad de Jaén; la Universidad de Zaragoza; la Universidad Nacional de Educación a Distancia; la Universidad Politécnica de Madrid y la Universidad Rovira i Virgili.Presidente: Rafael Vázquez Valenzuela.- Secretario: Claudio Bombardelli.- Vocal: Bruce A. Conwa

Treatments of proximal upper extremity amputations : utility of hand allotransplantation versus myoelectric prostheses

Les amputations d’un membre supérieur sont non seulement dévastatrices pour le bien-être physique, psychologique et social des patients, mais elles comportent également des répercussions financières importantes pour l’individu et le système de santé. Les allotransplantations de tissus composites vascularisés ont été proposées en tant que solution permettant de rétablir la forme et la fonction au détriment d’une immunosuppression à vie et d’un taux élevé de rejet chronique. Les prothèses myoélectriques combinent l’expertise chirurgicale avec les avancées technologiques pour réhabiliter les fonctions motrices d’un moignon amputé, mais elles demeurent limitées par un taux élevé d’abandon et des coûts importants. Dans les systèmes de santé avec des ressources limitées, les dirigeants ont la tâche complexe de partager équitablement l’allocation de ressources entre plusieurs maladies et interventions. Dans le domaine de l’économie de la santé, les analyses de type coût-bénéfice ont été développées pour répondre à ces questions. Les mesures d’utilité doivent incorporer l’impact que le traitement suscite sur l’espérance de vie et la qualité de vie. Ces utilités sont ensuite rapportées en fonction du coût, ce qui permet aux dirigeants de la santé de déterminer dans quels traitements il serait préférable d’investir les ressources. Dans cette thèse, nous proposons un modèle pour étudier les coûts-utilité des allotransplantations de la main et des prothèses myoélectriques. Pour commencer, une étude pilote a été effectuée sur les amputations du pouce traitées avec des lambeaux libres de l’orteil, ce qui nous a permis de confirmer la faisabilité des questionnaires d’utilité conçus. Par la suite, les utilités ont été mesurées dans une population d’amputés du membre supérieur, de patients réimplantés proximalement et de contrôles en santé. Les résultats démontrent que 1) les patients réimplantés rapportent la meilleure utilité avec les prothèses myoélectriques, 2) les amputés unilatéraux préfèrent significativement les prothèses myoélectriques également, et 3) aucune différence n’a été recelée entre les deux traitements chez les amputés bilatéraux. Au final, une analyse des coûts-bénéfices a été effectuée dans le contexte du système de santé canadien, démontrant que le traitement des patients amputés unilatéralement avec des prothèses myoélectriques permettrait de sauver davantage de coûts, alors que l’écart en épargnes monétaires se rétrécit pour les amputés bilatéraux traités avec une allotransplantation ou une prothèse. Avec les résultats rapportés dans cette thèse, nous pouvons proposer une mise à jour des indications de traitements pour les patients avec une amputation du membre supérieur. Basé sur l’analyse de type coût-utilité, nous concluons que les amputés unilatéraux sont de meilleurs candidats pour des prothèses myoélectriques, alors que les deux traitements sont encore adéquats pour les amputations bilatérales.Amputations of the upper extremity are not only devastating for the patient’s physical, psychological and social well-being, but they also yield significant financial repercussions to the individual and the healthcare system. Vascularized composite allotransplantations of the upper extremity were proposed as a solution to restore form and function, albeit to the detriment of lifelong immunosuppression and high rates of chronic rejection. New-generation myoelectric prostheses combine surgical prowess with technological refinements to rehabilitate motor functions of the amputated stump, but remain plagued by high rates of abandonment and significant costs. In healthcare systems wherein resources are limited, financial regulators have the difficult task of proposing an equitable divide of resource allocations between a multitude of diseases and interventions. In the field of health economics, cost-benefit analyses were developed to assist in this decision-making process. Utility outcome measures need to encompass the impact that a treatment elicits on life expectancy and quality of life. Comparison of utilities of different interventions as a function of cost further indicates which route healthcare regulators should partake. In this thesis, we propose a model to study cost-utilities of hand allotransplantation and myoelectric prostheses. To begin, a pilot study was performed on thumb amputations treated with free toe flaps, which allowed to confirm the feasibility of the utility questionnaires that we developed. Afterwards, utilities and quality adjusted life years were measured in a population of upper extremity amputees, proximally replanted patients and healthy controls. Findings demonstrated that 1) replanted patients reported the highest utility outcomes for myoelectric prostheses, 2) unilateral amputees significantly preferred myoelectric prostheses as well, and 3) no significant preference between both interventions was obtained in patients with bilateral amputations. Finally, a cost-benefit analysis was performed in the context of the Canadian healthcare system, demonstrating that significant savings can be achieved with treatment of unilateral amputations with myoelectric prostheses, whereas the gap in cost savings between both treatment groups becomes less significant in bilateral amputees. With the findings reported in this thesis, we can propose an update of the indications for treatment in patients with upper extremity amputations. From the perspective of cost-utility analyses, we conclude that unilateral amputees are better candidates for myoelectric prostheses, and that both treatments can still be offered in cases of bilateral amputations

A Blueprint for Promoting Innovation, Interdisciplinary Teamwork, and Collaboration

In response to the myriad of pressures we are experiencing across the higher education landscape, many colleges and universities are exploring different ways to manage and drive change within their institutions. Centres for Teaching and Learning (CTLs) are well-positioned to be high-impact drivers of change in this evolving educational arena. With this comes the expectation that they will emulate and promote innovative practices and creative approaches when addressing many of our most complex academic challenges. Increased agility, cooperation, and strategic foresight within these centres are necessary to detect, respond, and adapt to anticipated future changes and disruptions. However, coordinating such a broad array of resources among CTL departments coupled with interpersonal implications often associated with organizational change and transformation can pose ongoing challenges for leadership. This Organizational Improvement Plan (OIP) will address these issues within the context of a teaching and learning centre at a mid-sized college in Southern Alberta. It will focus specifically on the fluctuating demands and functionality of the centre and the need for increased agility, cooperation, and collaboration among CTL departments to respond more effectively to our continuously shifting circumstances. This is accomplished by exploring the relational and systemic nature of the problem through the lens of complexity leadership theory and its three entangled leadership models: adaptive leadership, enabling leadership, and administrative leadership. The outcome is a strategy theoretically grounded in social cognition theory and a leadership model for cultivating adaptive capacity and leadership competence in strategic foresight

Towards sustainable agriculture in the developing world: Theoretical perspectives and empirical insights

This dissertation is based on the journal article format with a collection of four separate papers, three of which have been published. The objective of this dissertation is to offer perspectives to contextualize sustainable agriculture in relation to two societal contexts beyond farm and watershed: (1) the developing country context, and (2) the fresh fruit and vegetables (FFV) sector (with special reference to the agri-food standard called `Good Agricultural Practices\u27 (GAP) and Thailand). Papers in this dissertation thus aim to identify the social and ecological factors that help to define sustainable agriculture along these broader contexts

IT quality and organization development: using action research to promote employee engagement, leadership development, learning, and organizational improvement

Within IT areas, Quality is often reduced to visions strongly influenced by operational and tactical instruments, relegating to minor dimensions crucial Organization Development (OD) aspects which sustain Learning, and Innovation. The current Program, grounded on the relevance of these aspects, has targeted, within a Bank’s IT Division, an approach to induce organizational change, and to produce strategic actions and behavioural changes which have led to an effective improvement on Customers, and Employees’ Satisfaction. It has followed an Action Research paradigm – addressing a complex, transformational, planed change, and using a multidimensional, integrative approach, based on a holistic, open systemic view – not targeting for the development of new theories, but, mainly, the fulfilment of existing empirical, and methodological gaps. It has integrated a two-cycle OD approach, where a first cycle focused on Service Culture, Leadership, and Employee Engagement has developed the conditions for a second cycle based on the acquired knowledge (double loop) and devoted to strategy implementation. Although the intervention’s achievements cannot be generalized outside the context, they can be transposed to other settings. They’ve revealed important Management Implications which form the relevance basis for this doctoral dissertation, namely a holistic, values-based, and participative framework to address organizational transformation, and the associated critical success factors. An opportunity exists to further research in the field, linking together an OD approach with a TQM approach to organizational excellence. Also, a metamodel of the Action Research process which has been followed – evidencing, at a conceptual level, the main sub-processes, data groups, and linking points between the action and the research dimensions – has been produced. An opportunity exists for further research on the development of this metamodel, including a conceptual data model and a system behavioural perspective (responding to events).Nas áreas de TI, a Qualidade é frequentemente reduzida a visões fortemente influenciadas por instrumentos táticos e operacionais, menorizando aspetos de Desenvolvimento Organizacional (DO) que são essenciais para sustentar a Aprendizagem e a Inovação. O presente programa, alicerçado na relevância destes aspetos, visou, no contexto da Divisão de TI de um Banco, desenvolver uma aproximação indutora de mudança organizacional; produzindo ações de índole estratégica e mudanças comportamentais; tendo conduzindo a um incremento significativo na Satisfação de Clientes Internos e de Colaboradores. Um primeiro ciclo – focado na Cultura de Serviço, na Liderança e no Envolvimento dos Colaboradores – criou as condições para num segundo ciclo, baseado no conhecimento organizacional adquirido, e nas decisões estratégicas emergentes (“double loop” learning), proceder à respetiva implementação. Foi seguido um paradigma de Investigação-Ação – endereçando uma mudança complexa, transformacional, planeada; usando uma abordagem multidimensional e integrativa; baseada numa perspetiva holística e de sistemas abertos – não visando diretamente o desenvolvimento de novas teorias, mas, fundamentalmente o colmatar de lacunas de índole empírica e metodológica. Embora os resultados obtidos não possam ser generalizados fora do contexto, eles podem, contudo, ser transpostos para outras intervenções; evidenciando-se como importantes Implicações para a Gestão que integram a base de relevância desta tese: um Quadro de Referência para a Transformação Organizacional Holística, Participativa e Baseada em Valores e respetivos Fatores Críticos de Sucesso. Numa perspetiva de Desenvolvimento Organizacional abrem-se ainda oportunidades de investigação-ação futura, no mesmo contexto, progredindo para uma abordagem à Qualidade Total e à Excelência Organizacional. Para além disso, outro dos resultados relevantes da investigação corresponde à produção do Metamodelo do Processo de Investigação-Ação que foi seguido – evidenciando, ao nível conceptual, os seus principais subprocessos, grupos de dados e pontos de articulação entre a vertente de ação e a vertente de investigação. Nesta vertente, abrem-se ainda oportunidades de investigação futura em termos de desenvolvimento do metamodelo, por forma a incluir uma visão conceptual de dados e uma perspetiva comportamental de sistema (resposta a eventos)