Abstract
This paper illustrates the analysis of the collective dimension of the mathematical activity carried out in a didactic setting. Using as main tool the Herbartian schema enriched with some of the study dialectics (Chevallard 2008, 2009, 2011), our analyses focus on two empirical cases, both taken from online didactic processes: a study and research paths for teacher education carried out in an online and at distance modality, and a mathematical open forum were spontaneous and outside school didactic processes take place.