Visual Detection of Structural Changes in Time-Varying Graphs Using Persistent Homology

Topological data analysis is an emerging area in exploratory data analysis and data mining. Its main tool, persistent homology, has become a popular technique to study the structure of complex, high-dimensional data. In this paper, we propose a novel method using persistent homology to quantify structural changes in time-varying graphs. Specifically, we transform each instance of the time-varying graph into metric spaces, extract topological features using persistent homology, and compare those features over time. We provide a visualization that assists in time-varying graph exploration and helps to identify patterns of behavior within the data. To validate our approach, we conduct several case studies on real world data sets and show how our method can find cyclic patterns, deviations from those patterns, and one-time events in time-varying graphs. We also examine whether persistence-based similarity measure as a graph metric satisfies a set of well-established, desirable properties for graph metrics

Options for Securing RTP Sessions

The Real-time Transport Protocol (RTP) is used in a large number of different application domains and environments. This heterogeneity implies that different security mechanisms are needed to provide services such as confidentiality, integrity, and source authentication of RTP and RTP Control Protocol (RTCP) packets suitable for the various environments. The range of solutions makes it difficult for RTP-based application developers to pick the most suitable mechanism. This document provides an overview of a number of security solutions for RTP and gives guidance for developers on how to choose the appropriate security mechanism

Comparison of Interactive Visualization Techniques for Origin-Destination Data Exploration

Origin-Destination (OD) data is a crucial part of price estimation in the aviation industry, and an OD flight is any number of flights a passenger takes in a single journey. OD data is a complex set of data that is both flow and multidimensional type of data. In this work, the focus is to design interactive visualization techniques to support user exploration of OD data. The thesis work aims to find which of the two menu designs suit better for OD data visualization: breadth-first or depth-first menu design. The two menus follow Schneiderman’s Task by Data Taxonomy, a broader version of the Information Seeking Mantra. The first menu design is a parallel, breadth-first menu layout. The layout shows the variables in an open layout and is closer to the original data matrix. The second menu design is a hierarchical, depth-first layout. This layout is derived from the semantics of the data and is more compact in terms of screen space. The two menu designs are compared in an online survey study conducted with the potential end users. The results of the online survey study are inconclusive, and therefore are complemented with an expert review. Both the survey study and expert review show that the Sankey graph is a good visualization type for this work, but the interaction of the two menu designs requires further improvements. Both of the menu designs received positive and negative feedback in the expert review. For future work, a solution that combines the positives of the two designs could be considered. ACM Computing Classification System (CCS): Human-Centered Computing → Visualization → Empirical Studies in Visualization Human-centered computing → Interaction design → Interaction design process and methods → Interface design prototypin

Stochastic methods for measurement-based network control

The main task of network administrators is to ensure that their network functions properly. Whether they manage a telecommunication or a road network, they generally base their decisions on the analysis of measurement data. Inspired by such network control applications, this dissertation investigates several stochastic modelling techniques for data analysis. The focus is on two areas within the field of stochastic processes: change point detection and queueing theory. Part I deals with statistical methods for the automatic detection of change points, being changes in the probability distribution underlying a data sequence. This part starts with a review of existing change point detection methods for data sequences consisting of independent observations. The main contribution of this part is the generalisation of the classic cusum method to account for dependence within data sequences. We analyse the false alarm probability of the resulting methods using a large deviations approach. The part also discusses numerical tests of the new methods and a cyber attack detection application, in which we investigate how to detect dns tunnels. The main contribution of Part II is the application of queueing models (probabilistic models for waiting lines) to situations in which the system to be controlled can only be observed partially. We consider two types of partial information. Firstly, we develop a procedure to get insight into the performance of queueing systems between consecutive system-state measurements and apply it in a numerical study, which was motivated by capacity management in cable access networks. Secondly, inspired by dynamic road control applications, we study routing policies in a queueing system for which just part of the jobs are observable and controllable

Highlighting in information visualization: A survey

Highlighting was the basic viewing control mechanism in computer graphics and visualization to guide users' attention in reading diagrams, images, graphs and digital texts. As the rapid growth of theory and practice in information visualization, highlighting has extended its role that acts as not only a viewing control, but also an interaction control and a graphic recommendation mechanism in knowledge visualization and visual analytics. In this work, we attempt to give a formal summarization and classification of the existing highlighting methods and techniques that can be applied in Information Visualization, Visual Analytics and Knowledge Visualization. We propose a new three-layer model of highlighting. We discuss the responsibilities of each layer in the different stage of the visual information processing. © 2010 IEEE

Visualization Techniques for the Analysis of Neurophysiological Data

In order to understand the diverse and complex functions of the Human brain, the temporal relationships of vast quantities of multi-dimensional spike train data must be analysed. A number of statistical methods already exist to analyse these relationships. However, as a result of expansions in recording capability hundreds of spike trains must now be analysed simultaneously. In addition to the requirements for new statistical analysis methods, the need for more efficient data representation is paramount. The computer science field of Information Visualization is specifically aimed at producing effective representations of large and complex datasets. This thesis is based on the assumption that data analysis can be significantly improved by the application of Information Visualization principles and techniques. This thesis discusses the discipline of Information Visualization, within the wider context of visualization. It also presents some introductory neurophysiology focusing on the analysis of multidimensional spike train data and software currently available to support this problem. Following this, the Toolbox developed to support the analysis of these datasets is presented. Subsequently, three case studies using the Toolbox are described. The first case study was conducted on a known dataset in order to gain experience of using these methods. The second and third case studies were conducted on blind datasets and both of these yielded compelling results

From Social Simulation to Integrative System Design

As the recent financial crisis showed, today there is a strong need to gain "ecological perspective" of all relevant interactions in socio-economic-techno-environmental systems. For this, we suggested to set-up a network of Centers for integrative systems design, which shall be able to run all potentially relevant scenarios, identify causality chains, explore feedback and cascading effects for a number of model variants, and determine the reliability of their implications (given the validity of the underlying models). They will be able to detect possible negative side effect of policy decisions, before they occur. The Centers belonging to this network of Integrative Systems Design Centers would be focused on a particular field, but they would be part of an attempt to eventually cover all relevant areas of society and economy and integrate them within a "Living Earth Simulator". The results of all research activities of such Centers would be turned into informative input for political Decision Arenas. For example, Crisis Observatories (for financial instabilities, shortages of resources, environmental change, conflict, spreading of diseases, etc.) would be connected with such Decision Arenas for the purpose of visualization, in order to make complex interdependencies understandable to scientists, decision-makers, and the general public.Comment: 34 pages, Visioneer White Paper, see http://www.visioneer.ethz.c

A unified ontology-based data integration approach for the internet of things

Data integration enables combining data from various data sources in a standard format. Internet of things (IoT) applications use ontology approaches to provide a machine-understandable conceptualization of a domain. We propose a unified ontology schema approach to solve all IoT integration problems at once. The data unification layer maps data from different formats to data patterns based on the unified ontology model. This paper proposes a middleware consisting of an ontology-based approach that collects data from different devices. IoT middleware requires an additional semantic layer for cloud-based IoT platforms to build a schema for data generated from diverse sources. We tested the proposed model on real data consisting of approximately 160,000 readings from various sources in different formats like CSV, JSON, raw data, and XML. The data were collected through the file transfer protocol (FTP) and generated 960,000 resource description framework (RDF) triples. We evaluated the proposed approach by running different queries on different machines on SPARQL protocol and RDF query language (SPARQL) endpoints to check query processing time, validation of integration, and performance of the unified ontology model. The average response time for query execution on generated RDF triples on the three servers were approximately 0.144 seconds, 0.070 seconds, 0.062 seconds, respectively

Cycling as Reading a Cityscape: A Phenomenological Approach to Interface-Shaped Perception

This essay attempts to assess whether the perceptual issues posed by the contemporary interface culture, and the constant attitude shift demanded by the new media between the “natural” and the “as if” modes, might be considered a significant challenge for phenomenological aesthetics as understood in terms of Merleau-Ponty’s phenomenology of perception. To demonstrate how the use of a particular interface profoundly shapes the form and structure of an activity as well as enabling perception of a particular kind, the author does not focus directly on the state-of-the-art smart interfaces, but describes the experience of cycling in a large city, with the interface in the form of the bicycle upgraded with an imagined ride simulator. While the former enables a very particular entrance into the world of perception, shaped by its moderate speed and detachment from the ground, the latter enables techno-shaped perception in the “as if” screenic mode. The experience described raises questions concerning the kinaesthetic, proprioceptive and motor features contributing to the cyclist’s mobile perception, as well as pointing to issues related to the reading of the city’s network as a particular spatial configuration generated by the cyclist’s realtime activity. This is the space-time-event-ridescape maintained and modified by the corporeal act of cycling. The spatiality of such a ride does not presume the notion of a space that contains the cyclist, but builds on notions of being-in-the-ridescape (as a kind of cityscape), in terms not only of full corporeal and mental engagement, but also of bodily literacy. The reading of the cityscape enabled by the combination of two interfaces, the bicycle and the ride simulator, is discussed in relation to de Certeau’s account of pedestrian (walking) experience in a big city, his distinction between strategies and tactics, and the notion that each cyclist contributes a novel story to ridetext, which is viewed not as an aesthetic object but as the production of puzzles for the rider to solve. The paper cocludes by questioning the capacity of phenomenology to accommodate the contemporary phenomenon of a “mixed” or “augmented reality” either in concept or in relation to the demands of the phenomenological reduction and the ends of the epoché. Indo-Pacific Journal of Phenomenology, Volume 10, Edition 2, October 2010: 61-7