Quiz 3 (week 701)

Advantages of Packaged Data Models

-Use model components -Save time and cost -Less data model errors -Easier modify over time -Aid in requirements determination -Supertype/subtype hierarchies promote reuse -Many-to-many relationships enhance model flexibility -Vendor-supplied data model fosters integration with vendor's applications -Universal models support inter-organizational systems

Completeness Constraints

-Whether an instance of a supertype must also be a member of at least one subtype -Total Specialization Rule: Yes (double line) -Partial Specialization Rule: No (single line)

A ________ addresses whether an instance of a supertype may simultaneously be a member of two or more subtypes. A. disjointedness constraint B. disjoint rule C. partial specialization D. total specialization

A

Overlap-rule

AN instance of the supertype could be more than one of the subtypes ex: a temple person can be a worker and a student

Supertype Discriminator

An attribute of a supertype whose values determine the target subtypes

Disjoint Rule

An instance of the supertype can be only one of the subtypes. Ex; a patient can be either a resident or an out patient

Which of the following is a generic entity type that has a relationship with one or more subtypes? A. Megatype B. Supertype C. Subgroup D. Class

B

A ________ constraint is a type of constraint that addresses whether an instance of a supertype must also be an instance of at least one subtype. A. disjoint B. overlap C. completeness D. weak

C

An entity cluster can be formed by: A. abstracting a supertype and its subtype. B. combining directly related entity types and their relationships. C. combining a strong entity and its weak entities. D. All of these.

D

EERD

Enhanced entity relationship diagram

Generalization is a top-down process. True False

False

A member of a subtype does NOT necessarily have to be a member of the supertype. True False

True

A subtype can become a supertype if the subtype has other subtypes beneath it True False

True

A universal data model is a generic or template data model that can be reused as a starting point for a data modeling project. True False

True

An entity cluster can have a relationship with another entity cluster much the same way that an entity can have a relationship with another entity. True False

True

In a supertype/subtype hierarchy, attributes are assigned at the highest logical level that is possible in the hierarchy. True False

True

Specialization is the reverse of generalization. True False

True

10,12

pictures,questions

Entity Cluster

set of one or more entity types and associated relationships group into a single abstract entity type

Disjointness Constraints

tells whether an instance of a super type can be a member of 2 or more sub-types at the same time.

Generaliztion

the process of defining general entity type from a set of more specialized entity types. Bottom-up.

specialization

the process of defining one or more sub-types of the super type relationships -Top-down