3 Data Structures Initially, plankton surveys were included as
part of the trawl database. However, it soon became apparent
that the trawl data structures were not suitable for plankton
catch data. Therefore, a separate database, plankton, was
created that, at the conceptual level, is very similar to trawl
[Mackay, K. 1998: Marine Research database documentation. 6.
trawl. NIWA Greta Point Internal Report No. 6. 35p.], but has
attributes specific to plankton catches. This has the advantage
of allowing easy access to related trawl 3.1 Table Relationships
This database contains several tables. The ERD for plankton
(Figure 1) shows the physical data model structure [Also known
as a database schema.] of the database and its entities (each
entity is implemented as a database table) and relationships
between these tables. Each table represents an object, event, or
concept in the real world that has been represented in the
database. Each attribute of a table is a defining property or
quality of the table. All of the