Common information building blocks that are published and well-defined and that can be reused to create more complex data models and structures. Common Data Elements (CDEs) are standardized terms for the collection and exchange of data. CDEs are metadata; they describe the type of data being collected, not the data itself. See https://wiki.nci.nih.gov/display/caDSR/CTEP+Common+Data+Elements and https://cabig.nci.nih.gov/overview/caBIG_core_concepts