Pathways for Theoretical Advances in Visualization IEEE VIS 2016 Panel Min Chen∗ Georges Grinstein† Chris R. Johnson‡ University of Oxford, UK University of Massachusetts Lowell, USA University of Utah, USA Jessie Kennedy§ Tamara Munzner¶ Melanie Toryk Edinburgh Napier University, UK University of British Columbia, Canada Tableau Software, USA ABSTRACT • Taxonomies and Ontologies: In scientific and scholarly dis- ciplines, a collection of concepts are commonly organized There is little doubt that having a theoretic foundation will benefit into a taxonomy or ontology. In the former, concepts are the field of visualization, including its main subfields: information known as taxa, which are typically arranged hierarchically visualization, scientific visualization and visual analytics, as well as using a tree structure. In the latter, concepts, often in con- many domain-specific applications such as software visualization, junction with their instances, attributes, and other entities, are biomedical visualization, and so on. Since there has been a substan- organized into a schematic network, where edges represent tial amount of work on taxonomies and conceptual models in the various relations and rules. visualization literature, and some recent work on theoretic frame- works, such a theoretic foundation is not merely an airy-fairy am- • Principles and Guidelines: A principle is a law or rule that bition. In this panel, the panellists will focus on the question “How has to be followed, and is usually expressed in a qualitative can we build a theoretic foundation for visualization collectively as description. A guideline describes a process or a set of actions a community?” In particular, the panellists will envision the path- that may lead to a desired outcome, or actions to be avoided ways in four different aspects of a theoretic foundation, namely (i) in order to prevent an undesired outcome. The former usually taxonomies and ontologies, (ii) principles and guidelines, (iii) con- implies a high degree of generality and certainty of the causal- ceptual models and theoretic frameworks, and (iv) quantitative laws ity concerned, while the latter suggests that a causal relation and theoretic systems. may be subject to specific conditions. Keywords. Theory of visualization, information visualization, sci- • Conceptual Models and Theoretic Frameworks: The terms entific visualization, visual analytics, theoretical foundation, con- of frameworks and models have broad interpretations. Here cept, taxonomy, ontology, principle, guideline, model, measure- we consider that a conceptual model is an abstract represen- ment, framework, quantitative law, theoretic system. tation of a real-world phenomenon, process, or system, fea- turing different functional components and their interactions. 1 INTRODUCTION AND MOTIVATION A theoretic framework provides a collection of measurements and basic operators and functions for working with these mea- More than a decade ago, Johnson proposed “Theory of Visual- surements. The former provides a description of complex ization” as one of the top research problems in visualization [7]. causal relations in real world in a tentative manner, while the Since then there have been several focused events, including two latter provides a basis for evaluating different models quanti- panels in 2010 and 2011 respectively [18, 1], two workshops in tatively. 2010 (https://eagereyes.org/blog/2010/infovis-theory-workshop), and 2016 (https://sites.google.com/site/drminchen/home/events) • Quantitative Laws and Theoretic Systems: A quantitative respectively. However, it is still a common notion that “Theory of law describes a causal relation of concepts using a set of mea- Visualization” is a problem for a few individual researchers, and its surements and a computable function, which is confirmed un- solution, perhaps in the forms of some theorems or laws, may be der a theoretic framework. Under a theoretic framework, a too distant from practice to be useful. conceptual model can be transformed to a theoretic system through axioms (postulated quantitative principles) and theo- During the recent ATI Symposium on Theoretical Foundation of rems (confirmed quantitative laws). Unconfirmed guidelines Visual Analytics, the discussion on the need for building a theoret- are thus conjectures, and contradictory guidelines are para- ical foundation attracted a wide range of opinions, from “Visual- doxes. ization should not be physics-envy” to “It is irresponsible for aca- demics not to try.” Gradually, the attendees converged to a common understanding that a theoretical foundation consisted of several as- In the field of visualization, it is estimated that there are currently pects, and every visualization researcher should be able to make some thirty papers on taxonomies and ontologies; several hundreds direct contributions to the theoretical foundation of visualization. of principles and guidelines recommended by various books, re- In particular, the event identified four major aspects (cf. [8]): search papers, and online media; more than ten conceptual mod- els; a few theoretic frameworks; and a few quantitative laws that ∗e-mail: [email protected] are mathematically confirmed guidelines. There is little doubt that †e-mail: [email protected] much more effort will be required to address the problem of “The- ‡e-mail: [email protected] ory of Visualization” [7]. §e-mail: [email protected] Using the two questions (as shown in Figure 1) posed in the ATI ¶e-mail: [email protected] Symposium as an example, one may ask (i) what taxonomy would ke-mail: [email protected] encompass all concepts relevant to the two questions; (ii) what guideline could be followed by users in answering such a question in practice; (iii) what model could be used to represent and simulate a real world problem involving statistics, visualization, computa- tion, and interaction; or (iv) what quantitative measurement would £11.00 £10.50 Share Price of Company X £10.00 £9.50 classifications (taxonomies) arise over time due to differing opin- £9.00 When do we pause £8.50 £8.00 £7.50 ions of the importance of differentiating characteristics used in cre- £7.00 statistics and start £6.50 £6.00 £5.50 ating the concepts (taxa). This is usually as a result of new infor- £5.00 visualization? £4.50 2002 2003 2004 mation becoming available, often through technological advances. down sampling This can result in the same organism being classified according to different taxonomic opinions and subsequently have several alter- 100 101 102 103 104 105 106 107 108 109 native names, leading to miscommunication. Newer classifications number of data points in a time series are usually improvements on previous ones, but sometimes the ex- istence of alternative classifications reflects the fact that there is dis- agreement as to how to interpret the data on which the classification When do we pause is based. algorithmic computing Taxonomies play an increasing role in understanding in the field and start interaction? of visualization and provide a useful means for bringing order to the adding complexity range of existing visualization systems, tools, and techniques and are frequently adopted in literature surveys to categorise existing 100 101 102 103 104 105 106 107 108 109 work. There have been many taxonomies proposed in the visual- number of lines (or other units of complexity measurement) ization field focusing on different criteria, including taxonomies by data type/model, task (visual/user), visual representation/encoding, Figure 1: Two questions posed at the beginning of the ATI Sympo- interaction mechanism, user characteristics and combinations of sium on Theoretical Foundation of Visual Analytics. these often specialized by domain. The taxonomies have been de- veloped for aiding the design, selection or evaluation of visualiza- tion tools and techniques. I will present an overview of taxonomies enable us to estimate an optimal point of “when” in the two ques- in visualization and argue that we should consider taxonomy as an tions. These questions clearly suggest that a theoretical foundation investigative science, with taxonomic classifications representing needs more than a few theorems or laws, and the problem of “The- partial and evolving hypotheses rather than static identifications of ory of Visualization” should be solved through a collective effort of absolute taxa. Taxonomies are therefore fundamental tools to aid the VIS community, instead of a few individuals’ endeavour. our understanding and assist in the communication and develop- ment of the field of visualization. Main Topic. In this panel, we bring together visualization scien- tists with expertise in these four aspects. They will provide their Tamara Munzner on assessment of the state of the art in each aspect, identify gaps and Principles and Guidelines challenges, and outline opportunities and pathways. In comparison with the two previous panels (in 2010 and 2011), the panel will The depth and richness of the set of principles and guidelines that move on from the question about “why theory”, and will not dwell have been articulated within the visualization literature continues on the question of “which theory”. Instead, the panel will focus on to grow as the community matures. Writing a book allows a large “how to make new theoretical advances as a community”. scope for synthesizing and codifying knowledge [9, 12, 16, 17], and despite a profusion of many recent efforts we still need far more 2 PANEL FORMAT AND SCHEDULE of them