ERD Exam Questions and Answers4
What heuristic does Dr. H recommend for defining DKNF entities? - ANSWERS -One theme per
entity
Please draw an ERD of your choice (except not an example used in class). Include at least three
entities with key and non-key attributes and all appropriate relationships with their cardinalities.
- ANSWERS -
Please define "ERD," including its purpose and the names of the older data models it replaces. -
ANSWERS --ERD: Entity Relationship Diagram
-Purpose: is to model or define database structures
-Replaces: ERM(entity relationship model), Network data model, hierarchical data
model
What's the fundamental difference between DFDs and ERDs? - ANSWERS --ERD have structures
and are static
-DFD have processes and are dynamic
Please draw, name, and explain the purpose of the five symbols used in ERDs. - ANSWERS -
1)Labeled Rectangle: entity: a set of instances that share attributes
2)Labeled line: relationship: represents a relationship between two entities
3)Vertical slash: Cardinality indicator: cardinality of one
4)Circle: cardinality indicator: represents cardinality of zero
5)Crows foot: cardinality indicator: cardinality of many
What types of words are recommended to label entities? - ANSWERS -Nouns
What heuristic does Dr. H recommend for defining DKNF entities? - ANSWERS -One theme per
entity
Please draw an ERD of your choice (except not an example used in class). Include at least three
entities with key and non-key attributes and all appropriate relationships with their cardinalities.
- ANSWERS -
Please define "ERD," including its purpose and the names of the older data models it replaces. -
ANSWERS --ERD: Entity Relationship Diagram
-Purpose: is to model or define database structures
-Replaces: ERM(entity relationship model), Network data model, hierarchical data
model
What's the fundamental difference between DFDs and ERDs? - ANSWERS --ERD have structures
and are static
-DFD have processes and are dynamic
Please draw, name, and explain the purpose of the five symbols used in ERDs. - ANSWERS -
1)Labeled Rectangle: entity: a set of instances that share attributes
2)Labeled line: relationship: represents a relationship between two entities
3)Vertical slash: Cardinality indicator: cardinality of one
4)Circle: cardinality indicator: represents cardinality of zero
5)Crows foot: cardinality indicator: cardinality of many
What types of words are recommended to label entities? - ANSWERS -Nouns
