This document defines the use and structure of the Research Activity Identifier (RAiD) system. The RAiD system includes a registry which supports the identification of research projects, i.e. projects managed in a scholarly or industrial environment which are expected to lead to specified outputs.It also specifies the RAiD metadata record which holds key metadata relating to the identified project and indicates relationships to other entities and their persistent identifiers and metadata.RAiD is an identifier for research projects and sub projects or tasks within such projects. It is not itself an identifier for any individual, group or institution, it is not a repository for project documentation or deliverables, nor is it a repository, platform or storage method. It does not apply to research outputs.