Claims and assertions (TAN-c)

Many projects using the TAN format will need to include in their workflow general declarations that do not fit one of the TAN formats. In many cases, there are adequate formats that are available. At other times, you may want to encode your information in a format much like your other TAN files. For those cases, an experimental format, TAN-c, is provided.

The model is inspired by the Resource Description Framework (RDF; see the section called “Resource Description Framework (RDF) and Linked Open Data”). RDF depends upon a simple data model, where each datum consists of three items termed a subject, a predicate, and an object. The first and third are thought of as nodes, and the second as a connector between the nodes.


A connector, our preferred term, is frequently elsewhere called an edge, but that metaphor is confusing and misleading. A cylinder, for example, has two edges, but they don't connect anything we might think of as nodes. Furthermore, "edge" implies that what's really of interest is the surface of a three-dimensional object and the void beyond.

TAN was designed to serve scholars, who normally find simple declarative sentences—the strength of RDF—highly restrictive, absent any context or qualifiers. Claims always have a claimant. They are made at certain times, and are subject to doubt and nuance. Sometimes our claims are bare negation, e.g., "Aristotle was not the author of De mundo"—an assertion not possible to express in RDF.

TAN-c is conceived as a slightly more complex version of RDF. Every claim must be assigned to a claimant. The RDF terminology subject + predicate + object is adjusted by TAN RDF to subject + verb + object. Furthermore, claims may be tempered by certainty, and verbs may be modified by modals. The entire claim may be restricted to a particular time or place. If the object is data, the data type can be restricted by type and lexical form. Despite being somewhat more complex than RDF, TAN-c syntax is more human readable.

The root element of a TAN-c file is <TAN-c>.

The <declarations> takes <modal>, <person>, <place>, <unit>, <verb>, and <version>, all of which are described more thoroughly at Chapter 8, TAN patterns, elements, and attributes defined. Collectively, they provide the vocabulary that can used in the <body> of the file.

The <body> takes a required @claimant and @subject, which define the default values for the rest of the data.

The rest of <body> consists of a series of <claim>s.

<claim>s are allowed to nest. That is, it is possible to claim that X claims that Y claims that Z claims that.… by nesting <claim>s within each other.