Discourse Coherence Through the Lens of an Annotated Text Corpus: A Case Study

A corpus-based study of local coherence as established by anaphoric links between the elements in the thematic (Topic) and the rhematic (Focus) parts of sentences in different genres of discourse. The study uses the Czech data present in the Prague Dependency Treebank and annotated for surface and underlying syntactic relations, the contextual boundness of tree nodes (from which the bi-partition of the sentence into Topic and Focus can be derived) and the coreference and bridging relations. Among the four possible types of the relations between anaphoric links and the Topic-Focus bipartition of the sentence, the most frequently occurring type is a link between the Topic of the sentence to the Focus of the immediately preceding sentence. In case there is an anaphoric link leading from the Focus of one sentence to the Topic or Focus of the immediately preceding sentence, this link frequently leads from a contextually bound element of the Focus, which supports the assumption that it is convenient to distinguish between "overall" Topic and Focus and the local Topic and Focus and/or the anaphoric relation is of the type of bridging and the relationship is often interpreted as a contrast. As for the relationship between the relations of the Topic-to-Topic type, due to the word order typological difference for Czech and English, these relations in Czech are not at all related to the syntactic function of subject.