What rules govern tense usage in scientific articles?

This paper addresses the question of whether tense usage in EST discourse is governed by (a) rhetorical functions unique to a particular genre, for example, the genre of journal articles, or (b) the some temporal meanings governing tense choice in general English. It analyzes 20 articles from the Journal of Pediatrics and postulates that a comprehensive analysis of tense choice in EST discourse is needed that specifies a hierarchical relationship between context- dependent rhetorical functions, context-independent temporal meanings, and, finally, actual tense choices. Because this analysis outlines the optional rhetorical choices and obligatory temporal constraints affecting tense usage, it allows us to predict when authors can choose the temporal identity of a referent and when they cannot. Such an analysis highlights an important feature of EST discourse, which is that, under certain conditions, authors can choose the temporal identity of a referent depending on their rhetorical purposes.