When studying heritage artefacts and trying to represent what we know of them, it is important to portray not only key moments in evolution of artefacts, but also processes of transformation. In this contribution, we introduce a methodological framework of description of artefacts' transformation and investigate the usability and efficiency of diagrammatic representation as a mean to visualize the above mentioned framework. A focus of our interest is the way artefacts get transformed. The methodological proposal presented identifies as a central notion: a life cycle-a sum of states and transitions following in succession-in what can be seen as a diachronic approach. We then introduce the diagrams proposed in order to visualise the above mentioned life cycles and provide examples on major or minor architecture within the medieval part of the town of Kraków (former capital of Poland, experimental set for this research). Two types of diagrams are introduced: diachrograms that distribute along a time axis transitions and states, and variograms that detail the nature of the changes. A combination of these graphics should help better understanding, in a cleat-cut manner, how changes over time affect architecture. But it should also underline key aspects of data in " historical sciences " : uncertainties, incompleteness, long ranges of time, unevenly distributed physical and temporal stratigraphy. .