The hierarchy of salience of the items of the knowledge assumed by the speaker to be shared by him and by the hearer constitutes one aspect of a dynamic account of discourse (Sect. I). It is claimed that a representation of this hierarchy is a good support for discourse analysis (reference assignement, Sect. 2) and for discourse production (pronominallzatlon, definite description, Sect. 3).

1.1 In studying communication, it must be distinguished between the speaker's own image, the hearer's image and the assumptions the speaker has made about the hearer's image of the world. In the very process of discourse, the image of the world undergo changes of different kinds: new objects, relations, etc. are added to the repertoirs on the basis of the content of what has just been said, the universe of discourse may be restricted in that a certain of phenome:, a of a particular kind is marked as relevant for further discourse whereas the other elements are disregarded, or the salience (activation, foregrounding) of the items is changed in the sense of being easily accessible in memory (see Sgall, Haji~ ov~ and Panevov~, 1986, p. 54f). I% has been shown (Haji~ ov~ and Vrhov~, 1982; HajiSov~, 1987) that the changes of salience are dependent to a great extent on the topic/focus articulation of the utterance. As a matter of fact, most algorithms for anaphora resolution work with the notion of salience (el., eg, Hobbs, 1976; Sidner, 1979; Brennan, Friedman and Pollard, 1989); however, while in most of these approaches the degrees of salience are given only syntactically, the hierarchy of activation in our mode] is elso determined by the toplc/focus