Semantic Extents of Sketches

This paper investigates how an interpreter resolves a particular type of ambiguities common in sketches, namely, the ambiguities as to what graphical variables (such as line width in sketched maps) are expressive and what are not. We hypothesize that a graphical vari-able is assessed to be non-expressive if it has a unified value throughout the sketch (e.g. all bands representing roads have the same width in the sketch). Our experi-ment, which analyzed interpretative decisions of human subjects on sketches, has in fact demonstrates such an unfiedness effect, although an interesting collection of exceptions were also found. We discuss the implica-tions of these results, and offer the interpretation of the unfiedness effect as an evidence to the veristic disam-biguation strategy. Main Question Graphical representations can be ambiguous, just as sen-tences can. In the road-traffic map in Figure 1, for exam-ple, the label “Tampa ” can be attached either to the upper arrow or to the right-hand arrow, making the message about the direction to Tampa ambiguous. Also, many of Escher’s paintings exploit ambiguities of their crucial parts to create intriguingly paradoxical messages. Figure 1: An ambiguous traffic map. There is, however, a peculiar kind of ambiguity that seems more often the case about graphical representations tha