Extension of the type/token distinction to document structure

Abstract

The type/token distinction introduced by C. S. Peirce and taken up by many others is familiar when applied to individual symbols or characters in a writing system, and also when applied at a higher level to words (and word-like objects). Some writers apply the distinction not only at some basic or foundational level but also as a description of higher levels of organization. This paper follows their example by outlining a concrete extension of the type/token distinction to all levels of document organization, specifying that higher-level types may contain sequences of lower-level types, and similarly for higher- and lower-level tokens. We further extend the usual model of types and tokens by allowing higher-level types to contain not just sequences of (lower-level) types but also sets, bags, conjunctions and disjunctions of types. This allows the system to deal gracefully both with indeterminate documents (e.g., a manuscript in which it is not clear whether a given mark on the page represents a 'c' or a 't') and with intentionally polyvalent documents, in which some marks are to be read as tokens of more than one type, as in the “ambigram”, a sort of combination puzzle and calligraphic artwork in which the shapes on the page may be read in different ways, or the same way, in different directions. This account of document structure in terms of types and tokens is similar in many ways to that offered by SGML, XML, and other systems of descriptive markup. On this view, SGML and XML elements are, strictly speaking, types (and tokens) in Peirce's sense of those words. Some techniques developed in other areas to which the type/token distinction is relevant may be useful in work on markup languages (and vice versa).