Semantic Level

A framework for categorizing the depth of information conveyed in alt text descriptions of data visualizations, introduced by Lundgard and Satyanarayan. The four levels are: Level 1 (construction details such as chart type, axes, and encodings), Level 2 (statistical properties like extrema, correlations, and outliers), Level 3 (complex trends, patterns, and comparisons in the data), and Level 4 (domain-specific insights and societal context). Research with blind and low vision users has shown that Levels 1-3 are most useful for understanding scientific figures, making this framework a practical rubric for evaluating and improving alt text quality.