Claims and assertions (TAN-c)

Many projects using the TAN format will need to include in their workflow declarations about related concepts. 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 name is inspired by the W3C recommendation Resource Description Framework ( For some general background, 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. The second is frequently called an edge, but because that metaphor is confusing,


An "edge" suggests the limits of a single geometrical shape, against the void beyond. What is meant is to indicate that the predicate expresses the relationship between the subject and object, which, in the world of geometrical metaphors, is more like an arrow than an edge.

the term connector is preferred.

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

TAN-c is conceived as a slightly more complex version of RDF, where 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 its complexity, TAN-c is presented in a human-readable syntax, arguably more legible than current forms of RDF. See the detailed analysis of <claim> for examples.

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 in the links provided. Collectively, they provide the vocabulary available to 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.