Doctoral theses
Current Record: 21 of 125
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Identifier |
000454651 |
Title |
Analysis and visualization of directed graphs |
Alternative Title |
Ανάλυση και οπτικοποίηση κατευθυνόμενων γράφων |
Author
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Λιονάκης, Παναγιώτης Κ.
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Thesis advisor
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Τόλλης, Ιωάννης
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Reviewer
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Αργυρός, Αντώνιος
Στεφανίδης, Κωνσταντίνος
Τσαμαρδινός, Ιωάννης
Πρατικάκης, Πολύβιος
Liotta, Giuseppe
Μανασάκης, Κωνσταντίνος
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Abstract |
The display of Graphs, is widely used for the visualization of data or information.
Although it is important to show all the information represented by the edges and
the nodes of the graph, there are cases where this is either impossible due to the
complexity and the size of the graphs or even misleading since the graph could be
very dense, while other reasons may be related to privacy protection (e.g., social
network graphs). To overcome this challenge, different approaches imply to hide
the unnecessary or redundant information or even replace the original graph with a
subgraph or a summary.
The main objective of this dissertation is to investigate and elaborate on the visualization and analysis of large graphs. More specifically, regarding vizualization
we design and implement various versions of a new sophisticated framework of graph
layout techniques that focus on the idea of improving the visualization aesthetics,
in order to reduce the visualization complexity of the graph, on top of sophisticated
graph drawing layouts. These techniques can be categorized in two main groups. The
first category is with respect to bends while the second is based on edge removal. To
this respect, we perform a set of experiments that show that these techniques produce
progressively more abstract drawings of the input graph. No dummy vertices are introduced and the vertices of each path/channel are vertically aligned. Subsequently,
the value of the introduced approach is that it also provides a generic and parameterized visualization method based on the given scenario. Towards this direction, we
also elaborate on methods for grouping nodes with similar characteristics that naturally decomposes the graph based on the information derived by the edges within the
graph, which can be used in order to have better visualization of complex networks.
In order to evaluate our drawing layout techniques, we assess the usability of various versions of our new layout compared with the one produced by other hierarchical drawing techniques. As a result, we provide insights regarding the factors that affect
efficiency so introduce a set of metrics in order to evaluate the performance of these
techniques. Our algorithms require almost linear time. Moreover, we design and conduct a comparative task-based evaluation with users in which we ask the participants
to carry them out in order to extract the user's satisfaction level and exploit any
possible problems and difficulties as regards the reachability information. Generally,
the drawings produced by our algorithms have lower number of bends and are significantly smaller in area. The user evaluation also reveals that the performance of
the participants is slightly better in the drawings of our proposed model and that our
model is preferred in overall rating compared to the other model.
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Language |
English |
Subject |
Abstraction of edges |
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Bends |
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Crossings |
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Experimental and user study |
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Graph algorithms |
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Graph drawing |
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Hierarchical graph drawing |
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Information visualization |
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Reachability |
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Αλγόριθμοι γράφων |
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Αφαίρεση ακμών |
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Διασταυρώσεις ακμών |
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Κατευθυνόμενοι γράφοι |
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Οπτικοποίηση Πληροφορίας |
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Πειραματική έρευνα και έρευνα με χρήστες |
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Προσβασιμότητα |
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Σχεδίαση γράφων |
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Σχεδίαση ιεραρχικών γράφων |
Issue date |
2023-04-07 |
Collection
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School/Department--School of Sciences and Engineering--Department of Computer Science--Doctoral theses
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Type of Work--Doctoral theses
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Permanent Link |
https://elocus.lib.uoc.gr//dlib/6/3/5/metadata-dlib-1680260015-539028-22346.tkl
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Views |
876 |