W3C’s Ubiquitous Web Applications Working Group has published a Working Draft of Delivery Context Ontology. The Delivery Context Ontology provides a formal model of the characteristics of the environment in which devices interact with the Web or other services. The delivery context is an important source of information that can be used to adapt materials to make them useable on a wide range of different devices with different capabilities. The delivery context includes the characteristics of the device, the software used to access the service and the network providing the connection among others. This document describes the ontology (using OWL) and gives details of each property that it contains.