Data Modeling Concepts

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What is the primary objective of the Conference on Data Systems Languages (CODASYL) in creating the Database Task Group (DBTG)?

To establish database standards

What is the term for the collection of records in 1:M relationships in the Network Model?

Set

What is the purpose of the Data Definition Language (DDL) in the Network Model?

To define schema components

What is the term for the conceptual organization of the entire database as viewed by the database administrator?

Schema

What is an advantage of the Network Model?

Ability to model complex relationships

What is the relationship between the Owner and Member in the Network Model?

Parent-Child

What is the primary focus of physical/low-level data models?

Describing details of how data is stored in the computer

What is the purpose of the external schema in the Three-Schema Architecture?

To describe the various user views

According to the ANSI/SPARC framework, which level of abstraction describes the structure and constraints for the whole database?

Conceptual

What is the benefit of the Three-Schema Architecture in terms of program-data independence?

It supports changes to the physical storage without affecting the program

What is the role of the DBMS in the Three-Schema Architecture?

To map requests and data among schema levels

What is the main advantage of using implementation/representational/logical data models?

They balance user views with some computer storage details

What is the primary benefit of the declarative nature of SQL language?

Protection of data from programming errors

What is the main goal of Big Data management?

To derive business insights from large amounts of web-generated data

What is a key characteristic of NoSQL databases?

Supports distributed database architectures

What is the term for data with a large number of attributes but a low number of actual instances?

Sparse data

What is the term for the guarantee that updates will eventually propagate through the system?

Eventual consistency

What is the main characteristic of a key-value data model?

Has two main data elements: key and value

What is the primary focus of database vendors in the 'Internet age'?

Developing database products that interface efficiently with the Internet

What is a common characteristic of successful 'Internet age' databases?

Flexible, efficient, and secure Internet access

What type of data model provides concepts that are close to how users perceive data?

Conceptual / high-level / semantic data model

What is the main benefit of Object-Relational Data Models?

Provides upward compatibility with existing relational languages

Study Notes

Data Models

  • Also known as entity-based or object-based data models
  • Three types of data models:
    • Implementation/representational/logical data models
    • Physical/low-level data models
    • Conceptual/external/internal data models

ANSI/SPARC Three-Schema Architecture

  • Classified data models according to their degree of abstraction in the 1970s
  • Three levels of abstraction:
    • Internal schema: describes physical storage structures and access paths
    • Conceptual schema: describes the structure and constraints for the whole database for a community of users
    • External schema: describes the various user views

Mappings among Schema Levels

  • Needed to transform requests and data
  • Programs refer to an external schema and are mapped by the DBMS to the internal schema for execution

Object-Relational Data Models

  • Extend the relational data model by including object orientation and constructs to deal with added data types
  • Allow attributes of tuples to have complex types, including non-atomic values such as nested relations
  • Preserve relational foundations, in particular the declarative access to data, while extending modeling power
  • Provide upward compatibility with existing relational languages

Emerging Data Models: Big Data and NoSQL

  • Big Data: find new and better ways to manage large amounts of Web-generated data and derive business insight from it
  • Characteristics of Big Data:
    • High performance and scalability at a reasonable cost
    • Relational approach may not always match the needs of organizations with Big Data challenges
  • NoSQL databases:
    • Not based on the relational model
    • Support distributed database architectures
    • Provide high scalability, high availability, and fault tolerance
    • Support very large amounts of sparse data
    • Geared toward performance rather than transaction consistency

Key-Value Data Model

  • Two data elements: key and value
  • Every key has a corresponding value or set of values

Sparse Data

  • Number of attributes is very large
  • Number of actual data instances is low

Eventual Consistency

  • Updates will propagate through the system; eventually all data copies will be consistent

Evolution of Data Models

  • Each new data model capitalized on the shortcomings of previous models
  • Common characteristics:
    • Conceptual simplicity without compromising the semantic completeness of the database
    • Represent the real world as closely as possible
    • Representation of real-world transformations (behavior) must be in compliance with consistency and integrity characteristics of any data model

Data Models and Internet

  • Using internet as a prime business tool has drastically changed the role and scope of the database market
  • Characteristics of successful “Internet age” databases:
    • Flexible, efficient, and secure Internet access
    • Support for complex data types (video, audio) and relationships
    • Interfacing with multiple data sources and structures
    • Relative conceptual simplicity to make database design and implementation less cumbersome
    • A powerful DBMS graphical user interface (GUI) to help make the DBA’s job easier

Categories of Data Models and Data Abstraction Levels

  • Categories include:
    • Conceptual/high-level/semantic data models
    • Network model
    • Hierarchical model

Conceptual Data Models

  • Provide concepts that are close to the way many users perceive data
  • Created for the following objectives:
    • Represent complex data relationships more effectively than the hierarchical model
    • Improve database performance
    • Imposes a database standard

Network Model

  • 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

Understand the different types of data models, including entity-based, logical, and physical data models. Learn how ANSI/SPARC classifies data models according to their degree of abstraction.

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