The rectangular objects with heading depict database tables, where the heading contains the name of the table (e.g. “NUCLIDE”).
The rows under the heading list the data fields in a specific table (e.g. “A” or “Z” means mass number and proton number for a specific nuclide.
Regular data field.
Primary key data field; all primary keys together will uniquely identify the record.
Foreign key data field; references to a record of another table.
One-to-many relationship; depicts that many records of the second table may have reference to the same record of the first table.
In our example this means that more nuclear level entries may refer to the same nuclide.