The Quadruple Concept

Quadriga is based on the concept of Quadruples, also referred to as “contextualized triples,” which are quads with a structured fourth element. A detailed discussion of the Quadriga System and the concept of Quadruples can be found in [Damerow 2014].

What are Quadruples?

Quadruples are contextualized triples of the form <subject - predicate - object - context>. Quadruples, in contrast to triples, store contextual information about a subject, predicate, object statement. Such contextual information contains, for instance, which text was annotated or who annotated a text. The basic idea of Quadruples is similar to the notion of "quads" as described in [Macgregor and Ko 2003] or "nanopublications" as proposed by [Groth et al. 2010].

For what do you use Quadruples?

The concept of Quadruples has been created as a means to solve the problem of how "knowledge" can be represented on the web. Quadruples are used to represent texts as graphs. They are built on the idea that any statement can only be analyzed and interpreted in the context that the statement was made. In the Quadriga System, the context of a statement consists of the text the statement appears in, the text’s metadata, and information about the researcher reading and interpreting the text. However, the concept of quadruples is not limited to textual data, but can be applied to other forms of data as well (e.g. images).

What are Concepts?

Quadruples are used to define how "things" in a text relate to each other using <subject - predicate - object> relationships. Each part of such a relationship (subject, predicate, and object) refers to a so-called "Concept" that specifies the meaning of a term in a text. The Quadriga System uses an authority file system called Conceptpower that assigns Concepts a URL that is used to refer to them.


Damerow, Julia. 2014. "A Quadruple-Based Text Analysis System for History and Philosophy of Science." Dissertation. Arizona State University.

Groth, Paul, Andrew Gibson, and Jan Velterop. 2010. “The Anatomy of a Nanopublication.” Information Services and Use 30: 51-56.

Macgregor, Robert and In-Young Ko. 2003. “Representing Contextualized Data using Semantic Web Tools.” In International Workshop on Practical and Scalable Semantic Systems PSSS1.