25 Competencies are understood as a construct of skills, knowledge, and attitudes. The following framework unpacks different types of skills, knowledge, and attitudes that can facilitate participation of citizens in citizen science initiatives, as well as those of project initiators (including scientists, municipal employees, decision-makers, and policy-makers) to engage citizens in such initiatives. Each category of skills, knowledge, and attitudes may be relevant for one or more of the following actors: Those involvedwith management of data, including librarians and professional data management staff. Members of the general public participating in one or more steps of scientific research, typically as part of a collaborative project with professional scientists and other relevant actors. Those involved in setting up and/or running the citizen science initiative (including scientists, municipal employees, decision-makers, policy-makers, and citizens in case they assume that role). CS PI Citizen scientists Project initiators/facilitators Information professionals IP