Figure 4.2. Simplified sketch of the database structure (modified after Lazarus 1994). Each box represents one relational table, with field names listed in the box. Relational links between tables are shown by thin lines. Arrows point from a table with many records with the same value for the relating field, to a table with unique values for each record in this field. The primary key for each table (the combination of one or more fields which makes each record in the table unique) is underlined. The approximate number of records (as of February, 1998) is shown below each box. The records in the ‘Taxa by Hole’ table were extracted from the DSDP CD-ROM. The other tables were created by Neptune.