abstract: Node-link diagrams are widely used to visualize the relational structure of real world datasets. As identical data can be visualized in infinite ways by simply changing the spatial arrangement of the nodes, one of the important research topics of the graph drawing community is to visualize the data in the way that can facilitate people's comprehension. The last three decades have witnessed the growth of algorithms for automatic visualization. However, despite the popularity of node-link diagrams and the enthusiasm in improving computational efficiency, little is known about how people read these graphs and what factors (layout, size, density, etc.) have impact on their effectiveness (the usability aspect of the graph, e.g., are they easy to understand?). This thesis is comprehensive research to investigate the factors that affect people's understanding of node-link diagrams using eye-tracking methods. Three experiments were conducted, including 1) a pilot study with 22 participants to explore the layout and size effect; 2) an eye tracking experiment with 43 participants to investigate the layout, size and density effect on people's graph comprehension using abstract node-link diagram and generic tasks; and 3) an eye tracking experiment with the same participants to investigate the same effects using a real visualization analytic application. Results showed that participants' spatial reasoning ability had significant impact on people's graph reading performance. Layout, size, and density were all found to be significant effects under different task circumstances. The applicability of the eye tracking methods on visualization evaluation has been confirmed by providing detailed evidence that demonstrates the cognitive process of participants' graph reading behavior. / Dissertation/Thesis / Doctoral Dissertation Engineering 2015

<p>Za potrebe evaluacije kvaliteta vizuelizacije u svrhu prakse inkluzivnog dizajna razvijen je namenski jezik koji hendikepe vida opisuje kroz formalizam baziran na vizuelnim promenljivama. Namenski jezik se može koristiti kao dokumentacija, ili kao specifikacija hendikepa za posebno napisan simulator vizuelnih hendikepa koji se može koristiti za potrebe testiranja. Kao pandan ovoj tehnologiji razvijen je novi mehanizam za evaluaciju vizuelizacija koji kroz inovacije u metodologiji i statistici omogućava da se merodavni zaključci izvedu iz relativno malih uzoraka podataka.</p> / <p>For purposes of visualization quality evaluation as part of the practice of<br />inclusive design, a domain specific language was developed such that it<br />describes visual handicaps through a formalism based on visual variables.<br />This domain specific language can be used as documentation or as a handicap<br />specification for a specially constructed visual handicap simulator usable for<br />testing. Alongside this technology, a novel mechanism for visualization<br />evalution was developed. This mechanism allows, through innovations in<br />metholodoly and statistics, the production of trustworthy results from relatively<br />small data sets.</p>