Noting that conceptions of the cognitive representations and processes involved in discourse comprehension and production recently have undergone an important shift in orientation, this paper points out the importance of the shift to the conception of the nature of texts, of text understanding, and of cognitive processes in knowledge creation and written communication. The paper indicates that the shift replaces an earlier "text-centered" view in which the linguistic structure of a text is viewed as central to discourse processing with a "knowledge-centered" view, in which semantic structures for representing knowledge and cognitive processes for generating, manipulating, and communicating knowledge are seen as central. The paper points out that the shift re-introduces an earlier perspective on text comprehension as a constructive process, but also introduces precise models of semantic representation and processing and related models for the semantic analysis of discourse. These models lead to a more unified account of discourse comprehension, production, and other discourse processing abilities, and suggest certain new instructional approaches. It then discusses (1) the shift to a knowledge-centered theory of text comprehension and production, (2) semantic grammars and discourse analysis, (3) the production of semantic representations in writing, and (4) the creation of an environment for planning and analyzing semantic structures in writing. Appendixes contain examples of semantic discourse analysis procedures and text processing schematics. (FL)