4.3

Relationship Maxima

• Definition: The relationship maxima refers to the greatest number of instances of one entity that can relate to a single instance of another entity.

• Characteristics:

  • Each relationship has two maxima, one for each of the related entities.

  • Specified as one or many:

    • Singular: Maximum is one.

    • Plural: Maximum is many.

Relationship Minima

• Definition: The relationship minima refers to the smallest number of instances of one entity that can relate to a single instance of another entity.

• Characteristics:

  • Each relationship has two minima, one for each of the related entities.

  • Generally specified as:

    • Optional: Minimum is zero.

    • Required: Minimum is one.

Attribute Maxima and Minima

• Attribute Maxima: Refers to the maximum number of attribute values that can describe each entity instance.

• Attribute Minima: Refers to the least number of attribute values that can describe each entity instance.

Unique Attributes

• Definition: A unique attribute is different from a singular attribute.

• Characteristics:

  • A unique attribute can have at most one entity instance for each attribute value.

  • A singular attribute has at most one attribute value for each entity instance.

Steps to Document Relationships and Attributes

1. Determine Relationship Maxima and Minima

2. Determine Attribute Maxima and Minima

3. Identify Unique Attributes

4. Document Cardinality in glossary and, optionally, on ER diagram.