Modeling Data
Tags: #◇Conceptual #◇CCINFOM #◇ER Diagram #◇Data Modeling #◇M5
◇Key Definitions
Business Rules: Statements that define or constrain aspects of the business. Good business rules are declarative, precise, atomic, consistent, expressible, distinct, and business-oriented. Entity Instance: A single person, place, object, event, or concept (corresponds to a row). Entity Type: A collection of entities (corresponds to a table). Attribute: A property or characteristic of an entity type. Relationship Type: A meaningful association between entity types.
◇Theoretical Framework
Types of Attributes Simple vs. Composite: Simple cannot be broken down (e.g., Age). Composite can be (e.g., Address broken into Street, City). Single-Valued vs. Multi-Valued: A person can have one DOB but multiple Skills. Stored vs. Derived: DOB is stored, but Age can be derived from DOB and the current date. Identifier (Key): Uniquely identifies an entity instance. Can be simple or composite. Should not change in value, cannot be null, and should not contain intelligent information that might change.
Types of Entities Strong Entity: Exists independently and has its own unique identifier. Represented by a single-line rectangle. Weak Entity: Depends on a strong entity and cannot exist on its own. It has a partial identifier and is represented by a double-line rectangle. Associative Entity: An entity that acts as both a relationship and an entity. Used when a many-to-many relationship needs to have its own attributes or when it participates in other relationships.
Degree of Relationships Unary: One entity related to another of the same entity type (e.g., an Employee managing another Employee). Binary: Entities of two different types related to each other. Ternary: Entities of three different types related to each other.
Cardinality Constraints
Defines the number of instances of one entity that can or must be associated with each instance of another entity. Minimum Cardinality: If zero, the relationship is optional. If one or more, it is mandatory. Maximum Cardinality: The maximum number of related instances allowed (One-to-One, One-to-Many, Many-to-Many).
◇References & Navigation
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- Related Notes: ◇Introduction to Databases
ACTIVE RECALL VERIFICATION
Select an answer to verify conceptual comprehension and reveal the technical rationale.
Which term describes a single person, place, object, event, or concept in data modeling?
What type of attribute can be broken down into smaller, meaningful components like Street and City?
A person's "Age" can be calculated from their "Date of Birth" and the current date. What kind of attribute is "Age"?
Which of the following is a characteristic of a valid Identifier (Key)?
How is a Weak Entity visually represented in an Entity-Relationship (ER) diagram?
What type of entity acts as both a relationship and an entity, often used to resolve many-to-many relationships?
A relationship where entities of three different types are associated with each other is called a:
If an instance of an entity is not required to participate in a relationship, what is its minimum cardinality?
In a Unary relationship, the entity type is related to:
Which of the following is NOT a characteristic of a good business rule?