Logical Data Model

Entity Type

An entity type is any type of object for which we want to store data. In a logical data model, entity types represent the different objects or concepts we are interested in, such as customers, products, or orders.

Relationship Type

A relationship type is a named association between entities. It defines how entities are related to each other in the database. For example, a “works for” relationship may exist between an employee entity and a department entity.

Relation (Table)

A relation, also known as a table, is a data object defined by a set of attributes. In a database, relations store data records. For instance, an “employee” relation may have attributes like employee ID, name, and department.

Attribute (Column)

An attribute is a piece of information that describes a specific aspect of a data object. Attributes define the properties or characteristics of entities in a database. For example, in a “person” entity, attributes could include age, gender, and address.

Tuple (Row or Record)

A tuple, also known as a row or record, represents a single instance of a data object with specific values for all attributes in the relation. Each tuple in a relation corresponds to a unique data record. For instance, a tuple in a “course” relation could represent a specific course with values for attributes like course name, instructor, and schedule.