This chapter describes the role of convention in visual representation, which is essential not only in determining which objects are representations, but also in determining which visible properties of a symbol are correlated with properties of the referent. The chapter highlights the relevance of relations between symbol form and content, including resemblance. In this context, all visual representations stand in an isomorphic relation to the content they convey. Goodman's analysis of symbol systems identifies the differences between visual symbol systems, and shows what some visual symbols have in common with linguistic representations. Some visual representations in science have the syntactic character of text. Other figures have the syntactic and semantic features of pictorial representations. These results conflict with a tacit assumption that influence many of those trying to account for the difference between pictorial representations and text: the assumption that symbol types can be defined in terms of exclusive sets of properties. Isomorphic relations between symbol form and content determine the referents of individual symbols of a visual system. Such a relation holds between the form of the symbol and the features represented. In addition, Goodman's analysis might lead to a radical conclusion: in spite of the dramatic difference in how pictures look compared to text or diagrams, pictorial representations simply refer to very complicated properties..
Perini, L. (2005). 3 Convention, resemblance and isomorphism: understanding scientific visual representations. Studies in Multidisciplinarity, 2(C), 37–47. https://doi.org/10.1016/S1571-0831(04)80031-5