The descriptions of the individual database tables use the following conventions:
Superscript indexes
Primary keys are marked with the superscript index PK.
Unique keys are marked with the superscript index U.
If a table has multiple unique keys, the superscript index U has an additional ordinal number. Attributes that together form the same unique key, have the same number.
Example: attribute_one U1 , attribute_two U2 , attribute_three U2
References to fields in other tables
The description of a database table sometimes may contain a reference to an attribute of another database table. In this case, the expression [TABLE.ATTRIBUTE] is used to identify the referenced table and attribute. (This is regardless of whether relational integrity constraints are actually implemented on the database.)
Only validity constraints are listed
In the descriptions, constraints are listed in the “Validity” column only if an attribute may not take all values according to its data type.
Mandatory attributes do not have any default value
In the descriptions, if no default value is listed in the “Default” column, an attribute is mandatory.