The line is a graphical element widely used in data visualizations, its purpose often being to signal a connection between other visual elements. Based on social semiotic theory, this article investigates what semiotic functions connecting lines can have and how these functions can be related to variations in form. The results show that, in addition to the basic function of connecting elements, such lines can also indicate the level of certainty, direct the viewer to read the information either as a narrative or a conceptual claim, indicate patterns of cohesion, and regulate the viewer's position. These findings allow for further empirical research on the formation of visual conventions.

In data visualizations, connecting lines may have various semiotic functions, including the semiotic potential of indicating modality and uncertainty. The goal of this article is to find out how this semiotic potential is realized in current best practices of data visualizations and what conventions exist for the visual manifestations of these functions. This issue is addressed by using a corpus-based approach and a two-level analysis method within a social semiotic framework. First, the article offers a theoretical discussion on how the concepts of modality and uncertainty interrelate. Second, a method for investigating how these concepts are visualized at different levels is presented. Third, a corpus analysis including 163 award-winning data visualizations is presented. The results indicate the existence of certain conventions for visual modality markers, and thus offer new insights relevant for both design theory and practice.

For creating and reading data visualizations, visual literacy is crucial. This article advances the knowledge about graphical variations and conventions related to the basic graphical element of the graphical line used as a connector in data visualizations. Some visual characteristics of connecting lines can be used to show directionality and thus signal a narrative claim. Arrowheads may be one way to do so. However, particularly in a digital environment, other techniques may be used as well. This article presents a corpus study investigating the ways in which narrativity is signalled by connecting lines in current, publicly available digital data visualizations. The central connecting lines of 163 award-winning data visualizations are analysed with focus on their visual forms and how they represent actions and situations. The repeated occurrence of some visual techniques points to conventions formed both by a long tradition of analogue visualization and the advent of digital production techniques and output devices. The presented results are relevant to researchers, educators and practitioners in the data visualization field, as they provide novel empirical data on the use of an omnipresent graphical element.

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The line is a graphical element widely used in data visualizations, its purpose often being to signal a connection between other visual elements. Based on social semiotic theory, this article investigates what semiotic functions connecting lines can have and how these functions can be related to variations in form. The results show that, in addition to the basic function of connecting elements, such lines can also indicate the level of certainty, direct the viewer to read the information either as a narrative or a conceptual claim, indicate patterns of cohesion, and regulate the viewer’s position. These findings allow for further empirical research on the formation of visual conventions.