Entity-Relationship Modeling Flashcards

An entity that cannot be uniquely identified by its own attributes alone and depends on another entity is called a:

Answer: Weak entity

A weak entity lacks sufficient attributes to form its own primary key and relies on its owner (strong) entity for full identification.

In ER modeling, 'participation constraint' refers to:

Answer: Whether every entity instance must participate in a relationship (total) or participation is optional (partial)

Participation constraints specify whether all (total) or only some (partial) entity instances must participate in a given relationship.

What does a '1' on one side and an 'M' on the other side of a relationship line signify?

Answer: One-to-many relationship

A 1:M (one-to-many) relationship means one instance on the '1' side can be associated with multiple instances on the 'M' side.

Which of the following is TRUE about a recursive (unary) relationship?

Answer: It is a relationship where an entity type is associated with itself

A unary (recursive) relationship associates instances of a single entity type with each other, such as an Employee who manages other Employees.

When an ER diagram shows a relationship with an attribute (e.g., 'Date' on a WORKS_FOR relationship), what does this indicate?

Answer: The attribute describes a property of the relationship itself, not either entity alone

Relationship attributes capture information that only makes sense in the context of the association between two entities, not either entity individually.

In the Chen ER notation, a diamond shape represents:

Answer: A relationship type

In Chen notation, diamond shapes denote relationship types connecting two or more entity types.

Which type of attribute is depicted with a dashed underline in an ER diagram?

Answer: Discriminator (partial key) of a weak entity

A dashed underline marks the discriminator (partial key) of a weak entity, distinguishing it from a full primary key marked with a solid underline.