Scenario Approach for Parametric Markov Models

In this paper, we propose an approximating framework for analyzing parametric Markov models. Instead of computing complex rational functions encoding the reachability probability and the reward values of the parametric model, we exploit the scenario approach to synthesize a relatively simple polynomial approximation. The approximation is probably approximately correct (PAC), meaning that with high confidence, the approximating function is close to the actual function with an allowable error. With the PAC approximations, one can check properties of the parametric Markov models. We show that the scenario approach can also be used to check PRCTL properties directly – without synthesizing the polynomial at first hand. We have implemented our algorithm in a prototype tool and conducted thorough experiments. The experimental results demonstrate that our tool is able to compute polynomials for more benchmarks than state-of-the-art tools such as PRISM and Storm, confirming the efficacy of our PAC-based synthesis.</p

Propuesta metodológica para el cálculo de las penalidades por giro en modelos de accesibilidad

En esta tesis de maestría se busca desarrollar una metodología para el cálculo de las penalidades por giro a utilizar en los modelos de accesibilidad y en general en los modelos de transportes dada la utilización de algoritmos de caminos mínimos en el cálculo de los tiempos de viaje en la red vial que incluyen penalizaciones y restricciones por giro, entre estos la accesibilidad media global, utilizada en diversos temas como la planificación urbana y de transportes en Manizales (Colombia) y diferentes ciudades alrededor del mundo. En esta ciudad se han utilizado penalidades y restricciones por giro determinadas de manera subjetiva por lo que no se tiene un valor calculado a partir de un método científico. Por lo tanto, se calcularán las penalidades y restricciones por giro para la ciudad de Manizales realizando una cuantificación de los tiempos de giro de los vehículos en diversas intersecciones viales, escogidas a partir de un análisis de priorización y registrando un video en cada una. Con estos datos se podrá obtener el promedio de giro a izquierda y derecha, es decir, las penalidades por giro para Manizales a utilizar en los modelos de accesibilidad calculados en la ciudad o en general para los modelos de transportes. Las penalidades calculadas mediante está metodología serán comparadas con las penalidades utilizadas en investigaciones previas a través del gradiente de ahorro, el cual nos permite cuantificar las diferencias generadas por este dato y su importancia en los modelos de transportes, entre ellos la accesibilidadAbstract: In this Master’s degree thesis seeks develop a methodology for the calculation of turn penalties to use in accessibility models and in general for transport models given in the recent use of algorithms of shortest paths for the calculation of travel times in the road network that includes turn penalties and restrictions, among then the global mean accessibility, used in some issues such as urban and transport planning in Manizales (Colombia) and different cities around the world. At Manizales, turn penalties and restrictions used in accessibility models are determined by a subjective way, so there are not calculated from a scientific method. Therefore, turn and restrictions penalties for Manizales will be calculated, making a quantification of the turn times of the vehicles in different road intersections, chosen from a priorization analysis and recording a video in each one. With this data we can obtain the average time to turn to left and right, that is, the turn penalties for Manizales to be used in the accessibility models calculated in the city or in general in the transport models. The penalties calculated using this methodology will be compared with the penalties used in previous investigations through the saving gradient, which allows us to quantify the differences generated by this data and its importance in transport models, including accessibilityMaestrí

A criteria based function for reconstructing low-sampling trajectories as a tool for analytics

Abstract: Mobile applications equipped with Global Positioning Systems have generated a huge quantity of location data with sampling uncertainty that must be handled and analyzed. Those location data can be ordered in time to represent trajectories of moving objects. The data warehouse approach based on spatio-temporal data can help on this task. For this reason, we address the problem of personalized reconstruction of low-sampling trajectories based on criteria over a graph for including criteria of movement as a dimension in a trajectory data warehouse solution to carry out analytical tasks over moving objects and the environment where they moveMaestrí

Visual-auditory visualisation of dynamic multi-scale heterogeneous objects.

The multi-scale phenomena analysis is an area of active research that is connecting simulations with experiments to get a correct insight into the compound dynamic structure. Visualisation is a challenging task due to a large amount of data and a wide range of complex data representations. The analysis of dynamic multi-scale phenomena requires a combination of geometric modelling and rendering techniques for the analysis of the changes in the internal structure in the case of data coming from different sources of various nature. Moreover, the area often addresses the limitations of solely visual data representation and considers the introduction of other sensory stimuli as a well-known tool to enhance visual analysis. However, there is a lack of software tools allowing perform an advanced real-time analysis of heterogeneous phenomena properties. The hardware-accelerated volume rendering allows getting insight into the internal structure of complex multi-scale phenomena. The technique is convenient for detailed visual analysis and highlights the features of interest in complex structures and is an area of active research. However, the conventional volume visualisation is limited to the use of transfer functions that operate on homogeneous material and, as a result, does not provide flexibility in geometry and material distribution modelling that is crucial for the analysis of heterogeneous objects. Moreover, the extension to visual-auditory analysis emphasises the necessity to review the entire conventional volume visualisation pipeline. The multi-sensory feedback highly depends on the use of modern hardware and software advances for real-time modelling and evaluation. In this work, we explore the aspects of the design of visual-auditory pipelines for the analysis of dynamic multi-scale properties of heterogeneous objects that can allow overcoming well-known problems of complex representations solely visual analysis. We consider the similarities between light and sound propagation as a solution to the problem. The approach benefits from a combination of GPU accelerated ray-casting, geometry, optical and auditory properties modelling. We discuss how the modern GPU techniques application in those areas allows introducing a unified approach to the visual-auditory analysis of dynamic multi-scale heterogeneous objects. Similarly to the conventional volume rendering technique based on light propagation, we model auditory feedback as a result of initial impulse propagation through 3D space and its digital representation as a sampled sound wave obtained with the ray-casting procedure. The auditory stimuli can complement visual ones in the analysis of the dynamic multi-scale heterogeneous object. We propose a framework that facilitates the design of dynamic multi-scale heterogeneous objects visual-auditory pipeline and discuss the framework application for two case studies. The first is a molecular phenomena study that is a result of molecular dynamics simulation and quantum simulation. The second explores microstructures in digital fabrication with an arbitrary irregular lattice structure. For considered case studies, the visual-auditory techniques facilitate the interactive analysis of both spatial structure and internal multi-scale properties of volume nature in complex heterogeneous objects. A GPU-accelerated framework for visual-auditory analysis of heterogeneous objects can be applied and extend beyond this research. Thus, to specify the main direction of such extension from the point of view of the potential users, strengthen the value of this research as well as to evaluate the vision of the application of the techniques described above, we carry out a preliminary evaluation. The user study aims to compare our expectations on the visual-auditory approach with the views of the potential users of this system if it is implemented as a software product. A preliminary evaluation study was carried out with limitations imposed by 2020/2021 restrictions. However, it confirms that the main direction for the visual-auditory analysis of heterogeneous objects has been identified correctly and visual and auditory stimuli can complement each other in the analysis of both volume and spatial distribution properties of heterogeneous phenomena. The user reviews also highlight the necessary enhancements that should be introduced to the approach in terms of the design of more complex user interfaces and consideration of additional application cases. To provide a more detailed picture on evaluation results and recommendations introduced, we also identify the key factors that define the user vision of the approach further enhancement and its possible application areas, such as users experience in the area of complex physical phenomena analysis or multi-sensory area. The discussed in this work aspects of heterogeneous objects analysis task, theoretical and practical solutions allow considering the application, further development and enhancement of the results in multidisciplinary areas of GPU accelerated High-performance visualisation pipelines design and multi-sensory analysis

Zielorientierte Erkennung und Behebung von Qualitätsdefiziten in Software-Systemen am Beispiel der Weiterentwicklungsfähigkeit

The evolvability of software systems is one of the key issues when considering their long term quality. Continuous changes and extensions of these systems are neccessary to adjust them to new or changing requirements. But the changes often cause quality deficiencies, which lead to an increase in complexity or an architectural decay. Especially quality deficiencies within the specification or the architecture of a software system can heavily impair a software system.To counteract this, a method is developed in this work to support the analysis of a quality goal in order to identify the quality deficiencies which hinder the achievement of the quality goal. Both the detection and the removal of quality deficiencies are accomplished in a systematic way. The method integrates detection of these quality deficiencies and their removal by reengineering activities based on rules. The detection of quality deficiencies is performed by means of measurable quality attributes which are derived from a quality goal, such as evolvability. In order to demonstrate the practicability of the method, the quality goal evolvability is taken as an example. This work shows how a software system can be evaluated with regard to evolvability based on structural dependencies and which reengineering activities will improve the system in the direction of this quality goal.To evaluate the method, it was applied within an industrial case study. By analyzing the given software system a large number of different quality deficiencies were detected. Afterwards the system's evolvability was improved substantially by reengineering activities proposed by the method.Für unternehmenskritische Software-Systeme, die langlebig und erweiterbar sein sollen, ist das Qualitätsziel Weiterentwicklungsfähigkeit essentiell. Kontinuierliche Änderungen und Erweiterungen sind unabdingbar, um solche Software-Systeme an neue oder veränderte Anforderungen anzupassen. Diese Maßnahmen verursachen aber auch oft Qualitätsdefizite, die zu einem Anstieg der Komplexität oder einem Verfall der Architektur führen können. Gerade Qualitätsdefizite in der Spezifikation oder Architektur können Software-Systeme stark beeinträchtigen.Um dem entgegenzuwirken, wird in dieser Arbeit eine Methode entwickelt, welche die Einhaltung von Qualitätszielen bewerten kann. Dadurch wird sowohl das Erkennen als auch das Beheben von Qualitätsdefiziten in der Software-Entwicklung ermöglicht. Qualitätsdefizite werden anhand einer am Qualitätsziel orientierten und regelbasierten Analyse erkannt und durch zugeordnete Reengineering-Aktivitäten behoben. Als Beispiel für ein Qualitätsziel wird die Weiterentwicklungsfähigkeit von Software-Systemen betrachtet. Es wird gezeigt, wie dieses Qualitätsziel anhand von strukturellen Abhängigkeiten in Software-Systemen bewertet und durch gezielte Reengineering-Aktivitäten verbessert werden kann.Um die Methode zu validieren, wurde eine industrielle Fallstudie durchgeführt. Durch den Einsatz der Methode konnten eine Vielzahl von Qualitätsdefiziten erkannt und behoben werden. Die Weiterentwicklungsfähigkeit des untersuchten Software-Systems wurde durch die vorgeschlagenen Reengineering-Aktivitäten entscheidend verbessert