Conceptual model and the logical model
The conceptual model helps in the establishment of entities, their attributes, and their relationship. On the other hand, logical models define the structure of data elements and set relationships between them.
Conceptual Model Diagram
| Attribute | Type | Nullable |
| Id_movie | INTEGER | NOT NULL |
| Title | VARCHAR | NOT NULL |
| Genre | VARCHAR | NOT NULL |
| Rating | FLOAT | NOT NULL |
| Id_star | INTEGER | NOT NULL |
| Id_producer | INTEGER | NOT NULL |
| Id_director | INTEGER | NOT NULL |
Person:
| Attribute | Type | Nullable |
| Id_person | INTEGER | NOT NULL |
| Name | VARCHAR | NULL ALLOWED |
| Last Name | VARCHAR | NOT NULL |
Producer:
| Attribute | Type | Nullable |
| Id_producer | INTEGER | NOT NULL |
Director:
| Attribute | Type | Nullable |
| Id_director | INTEGER | NOT NULL |
Star:
| Attribute | Type | Nullable |
| Id_star | INTEGER | NOT NULL |
Explanation
The previously presented Conceptual Model is directly derived from the movie database used in the assignment. Although it may seem that a hierarchy is not useful, it is actually a powerful tool that allows the designer to model complex semantic such as a person being a director and also a producer for the same movie without adding data redundancy to the information being stored. However, there is a problem when modeling producers in a movie. A producer can be a person but also a company. This particular situation is not clearly modeled in the diagram above but can be solved using the fields inside the Producer entities to hold data such as a company name. Most of the notation used in this diagram was taken from the ER Model concepts.
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Logical Model
Logical Model Diagram
The logical model is directly derived from the Conceptual Model using rules defined in the Entity-Relationship Model. The resulting logical model is defined as followed:
Movie(id_movie, genre, rating, id_producer, id_director, id_star)
Person(id_person, name, last_name)
Producer(id_producer)
Star(id_star)
Director(id_director)
Underlined attributes are those defined as the primary key for the relation. Those written in italic are foreign keys. Referential integrity restrictions are defined using the following syntax:
SourceTable[Field_as_foreign_key]<<ReferencedTable[Field_as_primary_key]
Therefore, referential restrictions in the Logical Model defined above are:
Movie[id_producer]<<Producer[id_producer]
Movie[id_star]<<Star[id_star]
Movie[id_director]<<Director[id_director]
Director[id_director]<<Person[id_person]
Star[id_star]<<Person[id_person]
Producer[id_producer]<<Person[id_producer]
The only nullable attribute is the name from Person relation. It is done this way in order to support companies inside the producer relation.
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References
Elmasri, R., &Navathe, S. (2017). Fundamentals of database systems. 1272 Seiten: Verlagnichtermittelbar.
SILBERSCHATZ, A. (2019). DATABASE SYSTEM CONCEPTS. S.l.: MCGRAW-HILL EDUCATION.