DBTG and Database Standards

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Questions and Answers

What is a benefit of the navigational language in the Network Model?

Structural independence

Optimal navigation through the database (correct)

Promotes database integrity

Conformance to standards

What is a disadvantage of the Network Model?

System complexity (correct)

Data access flexibility

Handles more relationship types

Data independence

Who developed the Relational Model?

E.F.Codd (correct)

IBM

SQL Server

ORACLE

What is a characteristic of the Network Model?

Navigational and procedural Signup and view all the answers

What is a limitation of the Network Model?

Little scope for automated query optimization Signup and view all the answers

What is the primary objective of creating the Network Model?

To improve database performance and impose a database standard Signup and view all the answers

What is the function of the Subschema in the Database Task Group (DBTG) report?

Defines the database portion seen by application programs Signup and view all the answers

What is the term used to describe the relationship between records in the Network Model?

Set Signup and view all the answers

What is the advantage of the Network Model in terms of data relationships?

Ability to model complex relationships and represents semantics of add/delete on the relationships Signup and view all the answers

What is the purpose of the Database Task Group (DBTG) created by the Conference on Data Systems Languages (CODASYL)?

To define standard specifications for a database creation environment Signup and view all the answers

What is the role of the Data Management Language (DML) in the Network Model?

Defines data characteristics and data structure Signup and view all the answers

What is the purpose of Chen Notation?

Representing entity relationships graphically Signup and view all the answers

What is the limitation of the Entity Relationship Model?

All of the above Signup and view all the answers

What is the key feature of the Object-Oriented Data Model?

Abstraction of real-world entities with operations Signup and view all the answers

What led to the popularity of Object-Oriented Data Modeling?

Cost savings through code reusability Signup and view all the answers

What is the benefit of the Object-Oriented Model?

Data independence and integrity Signup and view all the answers

What is the purpose of classes in the Object-Oriented Model?

To group objects with similar characteristics Signup and view all the answers

Study Notes

Network Model

Developed as an alternative to the hierarchical model
Handles more relationship types than the hierarchical model
Provides data access flexibility and promotes database integrity
Conforms to standards
Uses navigational language with constructs like FIND, FIND member, FIND owner, FIND NEXT within set, GET, etc.
Allows programmers to navigate optimally through the database

Disadvantages of Network Model

Navigational and procedural nature of processing
System complexity
Lack of structural independence
Database contains a complex array of pointers that thread through a set of records
Little scope for automated "query optimization"

Relational Model

Developed by E.F. Codd (IBM) in 1970
First commercial system in 1981-82
Created to represent complex data relationships more effectively than the hierarchical model
Improves database performance
Imposes a database standard

Crucial Database Components (DBTG report)

Schema: Conceptual organization of entire database as viewed by the database administrator
Subschema: Defines database portion seen by application programs that produce desired information from data contained within the database
Data Management Language (DML): Defines data characteristics and data structure in order to manipulate the data
Schema Data Definition Language (DDL): Enables database administrator to define schema components
Subschema DDL: Allows application programs to define database components that will be used
DML: Manipulates database contents

Network Model Basic Structure

Resembles hierarchical model
Collection of records in 1:M relationships
Relationship is called a Set: Set is composed of at least two record types
Owner: Equivalent to the hierarchical model’s parent
Member: Equivalent to the hierarchical model’s child

Network Model Advantages

Ability to model complex relationships and represents semantics of add/delete on the relationships
Crow’s foot and Chen Notations can be used for graphical representation
Entity is mapped to a relational table
Entity instance (occurrence) is a row in the table
Entity set is a collection of entities at any time
Connectivity labels types of relationships
Diamond connected to related entities through a relationship line
Relationships are expressed using Chen notation
Relationship name is written inside the diamond

Entity Relationship Model

Advantages

Exceptional conceptual simplicity
Visual representation
Effective communication tool
Integrated with the relational data model

Disadvantages

Limited constraint representation
Limited relationship representation
No data manipulation language
Loss of information content

Object-Oriented Model

Developed by Hammer and McLeod in 1981 as a semantic data model (SDM)
Modeled both data and their relationships in a single structure known as an object
Basis of object-oriented data model (OODM)
OODM becomes the basis for the object-oriented database management system (OODBMS)
Object is described by its factual content
Includes information about relationships between facts within object and relationships with other objects
Subsequent OODM development allowed an object to also contain operations
Object becomes basic building block for autonomous structures

Object-Oriented Model Basic Structure

Object: abstraction of a real-world entity, contains operations and is self-contained and forms a basic building-block for autonomous structures
Attributes describe the properties of an object
Objects that share similar characteristics are grouped in classes
Classes are organized in a class hierarchy
Inheritance is the ability of an object within the class hierarchy to inherit the attributes and methods of classes above it

Advantages of Object-Oriented Model

Adds semantic content
Visual presentation includes semantic content
Database integrity
Both structural and data independence
Persistent programming languages based OODB target applications of that form that have high performance requirements

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Description

Learn about the objectives of the Database Task Group (DBTG) and its role in establishing database standards. Discover how DBTG improves database performance and represents complex data relationships. Explore the crucial components of a database according to the DBTG report.