Mark

An elementary entity capable of perception within a spatial substrate. In the visual design space, marks include points, lines, circles, and areas — the basic building blocks from which all visual representations are composed. A bar chart is constructed from rectangular marks positioned within a two-dimensional spatial substrate. In the sonic design space, marks might be individual tones, clicks, or speech phonemes. The concept is useful for understanding the granularity at which content can be perceived and adapted: when translating a visual chart to an auditory representation, the visual marks (bars) must be re-expressed as sonic marks (tones or spoken values) within the sonic spatial substrate (time). This formal decomposition helps identify what information may be lost or gained during cross-modal adaptation.