The concept of discourse topic also emerged from the theoretical framework of the Prague School linguists. In particular, as Witte (1983a) points out, Frantisek Danes showed that topics of successive sentences can be identified in relation to what Danes called a "hypertheme," in effect a discourse topic, which may or may not be explicitly stated in the text. The discourse topic is what the text, taken as a whole, is about.
Lautamatti (1978) demonstrates the relationship between sentences in a text and discourse topic. Sentence topics, which are units of meaning organized hierarchically in the text, make a semantic contribution to the development of the discourse topic. Lautamatti (1978: 71) puts it thus:
"The development of the discourse topic within an extensive piece of discourse may be thought of in terms of a succession of hierarchically ordered subtopics, each of which contributes to the discourse topic, and is treated as a sequence of ideas, expressed in the written language as sentences. We know little about restrictions concerning the relationship between sentences and subtopics, but it seems likely that most sentences relating to the same subtopic form a sequence. The way the written sentences in discourse relate to the discourse topic is ... called topical development of discourse."