Data Management Foundations 4.5
True (Values of a partition attribute indicate which partition subtype contains each entity instance. Ex: CreditType value "Debit" indicates the card is a DebitCard)
Each partition attribute value corresponds to one subtype. True False
Partition attribute
Each partition corresponds to a one of these of the supertype entity. This indicates which subtype entity each instance belongs to. Ex: StatusCode is a __________ of the Student supertype entity. Code 'U' indicates the student is an undergraduate, and code 'G' indicates the student is a graduate.
Four analysis steps:
1. Discover entities, relationships, and attributes 2. Determine cardinality 3. Distinguish independent and dependent entities 4. Create supertype and subtype entities
True (Subtypes of different partitions can overlap. Ex: A card can be both a credit card and Visa simultaneously)
An entity instance can be in two subtypes of different partitions. True False
False (Subtypes of a partition are mutually exclusive. Ex: A card cannot be both Visa and MasterCard, or Visa and Discover, at the same time)
An entity instance can be in two subtypes of the same partition. True False
Subtype Entity
An entity that represents a special case of another entity, called a supertype
False (Each partition corresponds to one partition attribute. Ex: CreditCard cannot also correspond to SponsorCode)
One partition attribute can correspond to several partitions. True False
Similar entities
These are entities that have many common attributes and relationships. These entities become subtypes of a new supertype entity, as in the animation below. Common attributes and relationships move to the new supertype entity. Attributes and relationships that are not shared remain with the subtype entities.
Partition
This denotation of a supertype entity is a group of mutually exclusive subtype entities. Subtype entities in this cannot share common instances. Ex: Undergraduate and graduate students are mutually exclusive subsets of students. UndergraduateStudent and GraduateStudent ________ the supertype entity Student.
Supertype Entity
This type of entity usually has several subtypes. Attributes of this entity apply to all subtypes. Attributes of a subtype do not apply to other subtypes or the this entity.
ISA relationship
When something is multiple things ex: an employee is a manager and a person it its called this
