This text presents the SDRT, a theory of formal discourse representation whose originality lies in the inclusion of rhetorical relations inferred with the help of linguistic and extralinguistic knowledge. After a short presentation of the foundations of this theory, I will discuss some extension and modification projects. By looking at the modifications needed to include dialog phenomena and by looking at some issues of theoretical nature, I will sketch the dynamics of the research conducted in the SDRT framework in the last few years. Then, I will show how the analysis of combinatorial aspects of the rhetorical relations can give rise to new relations, and I will argue that these new relations are useful for an adequate analysis of syntax and discourse phenomena.