Towards a model for diachronous and synchronous citation analyses

This paper gives an overview of the diachronous (prospective) and synchronous (retrospective) approach to ageing studies of scientific literature from the perspective of technical reliability, visualising the different aspects that can be analysed by the two approaches. The main objective is to deepen the understanding of the mechanism and the theory underlying the two aproaches, and is to show that the difference between the diachronous and synchronous model is not “just counting into opposite directions”. In this context, a stochastic model is presented showing that one and the same model can be used to describe both diachronous and synchronous perspectives of citation processes. On the basis of this model, it is explained how some diachronous and synchronous citation-based indicators can be re-calculated for changing publication periods and citation windows underlying their construction. The paper is concluded by several applications such as the definition and calculation of diachronous (prospective) and synchronous (retrospective) journal impact measures and other citation indicators used in research evaluation.