The RDA Working Group on Data Citation (WG-DC) brings together experts addressing the issues, requirements, advantages and shortcomings of existing approaches for efficiently identifying and citing arbitrary subsets of (potentially highly dynamic) data. It's recommendations are based upon on (1) timestamping and versioning changes to evolving data and (2) identifying arbitrary subsets by assigning PIDs to the queries selecting the according subsets and are applicable across all types of data, such as e.g. collections of files, relational databases, multidimensional data cubes or regions in images.