Data Models: Lesson 2 Flashcards
(40 cards)
Why is data models important?
To facilitate interaction between the designer, applications programmer and the end user.
Data models organizes data for various users
What are the 4 data model basic building blocks?
entity, attribute, relationship and constraints
What is a entity?
It is anything about which data are to be collected and stored
What is a attribute?
It is a characteristic of a entity
What is a constraint?
It is a restriction placed on the data
What are the sources of business rules?
Company manager, department manager, policy maker, written documentation and direct interaction with the end user.
What are the 3 types of written documentation in business rules?
Standards, procedures and operations manuals
Documenting and identifying business rules is important because?
Standardize the companys view on data
Constitutes a communication tool between the designer and the end user
Allows designer to understand the scope, role and nature of the data
Allows the designer to understand the businesses processes
Promote the creation of an accurate data model
What are the 5 different types of data models?
Hierarchical, Network, Relational, Entity relationship and object oriented
Why was the hierarchical model developed and what does it look like?
To manage large amounts of data for complex manufacturing projects and it looks like an upside down tree
What are the advantages of the hierarchical model?
Many of the hierarchical data model’s features formed the foundation for current data models
Its database application advantages are replicated, albeit in a different form, in current database environments
What are the disadvantages of the hierarchical model?
Complex to implement
difficult to manage
lacks structural independence
lack of standards
Why was the network model created?
To impose the standard for data bases
to improve database performance
it represents complex data relationships more effectively
What doe CODASYL stand for?
Conference on Data Systems languages
What does DBTG stand for?
Database Task Group
What is a schema in the network model?
It is a conceptual organization of the entire database as viewed by the database administrator
What does DML stand for and what does it do?
Data Management Language, it is used to define the environment where the data can be managed
What does DDL stand for and what does it do in the schema DDL?
Data Definition Language, it enables the database administrator to define schema components
What does subschema DDL so?
It allows the program application to define the database components that will be used
What are the 2 record types in the network model?
Owner and member
What are the disadvantages of the network model?
Too cumbersome
The lack of ad hoc query capability put heavy pressure on programmers
Any structural change in the database could produce havoc in all application programs that drew data from the database
Many database old-timers can recall the interminable information delays
What does RDBMS stand for?
Relational Database Management System
What is the most important function of the relational model?
It can hide the complexities of the relational model from the user
What does SQL stand for and what does it do?
Structured Query Language, it allows the user to specify what must be done without specifying how to do it
