Since the early developments of the 1980s, Hasan and her colleagues have laid a solid foundation in systemic functional semantics – both theory and description. Indeed, Hasan’s insights on message semantics and her contextually open semantic networks have extended beyond her semantic variation or integrated sociolinguistic research. One consequence of the productivity of this paradigmatic description of meanings has been the increasing applications in various discourse studies. To highlight this ‘extended’ use of semantic descriptions, we survey the use of semantic networks in discourse analysis, presenting an up-to-date retrospective review on the different uses of message semantics. By accounting for the various domains of application, we seek to exemplify in what ways message semantic networks are employed by discourse analysts to tackle various research problems, enabling discourse analysts to understand ‘the nature of the relationship between language and society’ and ‘how and why language works’ (Hasan 2005:56). This chapter thus demonstrates one claim, namely that Hasan’s message semantics network is essentially a discourse analytical tool enabling discourse analysts to study language in use in various contexts.