Questions and Answers
What is a supertype in the context of entity modeling?
A generic entity type with a relationship to one or more subtypes
What is a subtype in the context of entity modeling?
A subgrouping of entities in an entity type with distinct attributes
What is a basic notation for supertype/subtype in entity modeling?
Microsoft Visio notation
What is attribute inheritance in the context of entity modeling?
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What is a completeness constraint in the context of supertype/subtype relationships?
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Study Notes
Supertype and Subtype in Entity Modeling
- A supertype is a higher-level entity that encompasses multiple subtypes, sharing common attributes and characteristics.
- A subtype is a specialized version of a supertype, inheriting all attributes from the supertype and possibly adding new ones.
Notation for Supertype/Subtype
- A basic notation for supertype/subtype in entity modeling is to represent the supertype as a rectangle, and the subtypes as rectangles connected to the supertype with a line.
Attribute Inheritance
- Attribute inheritance refers to the process by which a subtype inherits all attributes from its supertype, and can also add new attributes or override existing ones.
Completeness Constraints
- A completeness constraint in the context of supertype/subtype relationships ensures that every instance of the supertype must be an instance of at least one subtype.
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