In this chapter，the notion of global coherence is conceptualized as the global topical structure of the discourse.It is realized through a hierarchically organized set of topics at various levels.The discussion in this chapter shows that this notion can be beneficially extended to multimodal discourses which incorporate verbal，pictorial and graphical elements.

In the English learning advertisements，the overall discourse topic commands the hyper-topics of its component stages which in turn command topics of lower-level units.This embedded，hierarchical representation of discourse topics in the macro-structure in the textual analysis confirms van Dijk and Kintsch's（1983）assumption that schema in reader's mind“cannot be represented simply as one huge interrelated network of nodes，but that there must be subsets of that network that can function as wholes”（ibid：47）.

The topical structure represented by these semiotic configurations in various stages in the English learning advertisements constitutes the global coherence of the discourse which guides the processing and comprehension of the readers in an ordered and organized way.The overarching macro-Topic predicts and commands the hyper-Topics which in turn predicts and commands the Topics at a lower level in the hierarchy.These topics of various levels are made use of by the reader's mental frame to expect his or her processing of the local coherence relations and cohesive relations in the details of the text.During the reading process the incoming information in the local ranges of texts will provide on-line checking for the existing mental frame in the reader's mind.This interaction renders the comprehension process a dynamic and rewarding activity.