AnnotationUnit was introduced to account for annotating strings (selected according to certain criteria) directly with discourse information. Where structured elements (e.g., from syntax or semantics) represent the basis of annotation, the annotations should be directly anchored with them. Here, we are concerned with discourse annotation only. Syntactically or semantically defined units of annotations are thus considered opaque objects, as these are to be described in terms of the OLiA Reference Model.