## The model: an ordered hierarchy of citable objects

Citable texts are modelled as a set of citable nodes, each with four properties:

• each node belongs to a citation hierarchy
• each node belongs to a work hierarchy
• nodes are ordered within a single text
• nodes may have richly structured textual content

For historical reasons, this model is known as OHCO2.

### Citing texts

The semantics of the CTS URN is based on a model of citable text as an “Ordered Hierarchy of Citation Objects.”

## The ohco2 library

ohco2 is a cross-platform library written in Scala for working with repositories of citable texts.