Lecture 3 Flashcards
(21 cards)
What is a data model?
Relatively simple representations, usually graphical, of complex real-world data structures
Data models facilitate interaction among the designer, the applications programmer, and the end user.
What are business rules?
Brief, precise, and unambiguous descriptions of policies, procedures, or principles within a specific organization
Business rules apply to any organization that stores and uses data to generate information.
What is an entity in data modeling?
Anything about which data are to be collected and stored
What is an attribute in data modeling?
A characteristic of an entity
What is a relationship in data modeling?
Describes an association among entities
Fill in the blank: A _______ is a restriction placed on the data.
constraint
What are the types of relationships in data modeling?
- One-to-many (1:M) relationship
- Many-to-many (M:N or M:M) relationship
- One-to-one (1:1) relationship
What must business rules be rendered in?
Writing
True or False: Business rules must be easy to understand and widely disseminated.
True
What sources can business rules be discovered from?
- Company managers
- Policy makers
- Department managers
- Written documentation
- Procedures
- Standards
- Operations manuals
- Direct interviews with end users
What do nouns generally translate into when discovering business rules?
Entities
What do verbs generally translate into when discovering business rules?
Relationships among entities
What are the major data models that evolved?
- Hierarchical
- Network
- Relational
- Entity relationship
Who developed the relational model?
Codd (IBM) in 1970
Why was the relational model considered impractical in 1970?
Computers lacked power to implement the relational model
What does a relational table consist of?
A matrix consisting of a series of row/column intersections
What does an entity relationship diagram (ERD) represent?
Graphical representation of entities and their relationships in a database structure
What is an entity instance in a relational table?
A row in the table
What is an entity set?
Collection of like entities
Fill in the blank: The _______ is a logical structure that resembles a file.
relational table
What is the primary focus of the entity relationship model?
Graphical representation of entities and their relationships in a database structure
