The internal representation we have chosen is fairly straightforward and standard. Each XML element and piece of text is represented as a Java object. Each object consists of pairs of properties and an associated value .
Properties generalise the attributes of an XML element.
As an extension to the DOM model DTDs are also represented as objects. The types of nodes and their interrelationships are shown below. We have made one major extension to the DOM model of XML structure in order to support multiple documents and overlapping hierarchies, which as argued above, are needed to describe multiple speaker and multiple levels of annotation in dialogue corpora. We support this by allowing nodes in the IR to have multiple parents. Each node has a privileged parent which is the parent element in the same file as the node.