The core entities of a Study (its "keys") are Participants (identified by "Participant IDs") and Visits (identified by "Visit IDs" or "SequenceNums").
Participants appear at planned locations (Sites) at expected points in time (Visits) for data collection. At such Visits, scientific personnel collect Datasets (including Clinical and Assay Datasets) and Specimens. These are all uploaded or copied to the Study.
Participant/Visit pairs are used to uniquely identify Datasets and Specimens. Optionally, Sites can also be used as "keys." In this case, Participant/Visit/Site triplets uniquely identify Specimens.
A Study also tracks and manages Specimen Requests from Labs, plus the initial delivery of Specimens from Sites to the Specimen Repository.
Studies can be customized via the flexible definition of Visits (time points), Visit Maps (measurements collected at time points) and Schemas (data types and relationships).
The project team is free to define the additional Study entities as needed.