Database Fundamentals- Content Analysis

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Database Principles: Fundamentals of Design, Implementations and Management

CHAPTER 2: DATA MODELS

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

In this chapter, you will learn:

Why data models are important

About the basic data-modeling building blocks

What business rules are and how they influence database design

How the major data models evolved

How data models can be classified by level of abstraction

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

The Importance of Data Models

Data models

Relatively simple representations, usually graphical, of complex real-world data structures

Facilitate interaction among the designer, the applications programmer, and the end user

End-users have different views and needs for data

Data model organizes data for various users

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

Data Model Basic Building Blocks

Entity - anything about which data are to be collected and stored

Attribute - a characteristic of an entity

Relationship - describes an association among entities

One-to-many (1:*) relationship

Many-to-many (*:*) relationship

One-to-one (1:1) relationship

Constraint - a restriction placed on the data

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

Business Rules

A business rule is a brief, precise, and unambiguous descriptions of a policies, procedures, or principles within a specific organization

Apply to any organization that stores and uses data to generate information

Description of operations that help to create and enforce actions within that organization’s environment

Must be rendered in writing

Must be kept up to date

Sometimes are external to the organization

Must be easy to understand and widely disseminated

Describe characteristics of the data as viewed by the company

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

Discovering Business Rules

Sources of Business Rules:

Company managers

Policy makers

Department managers

Written documentation

Procedures

Standards

Operations manuals

Direct interviews with end users

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

Translating Business Rules into Data Model Components

Standardize company’s view of data

Constitute a communications tool between users and designers

Allow designer to understand the nature, role, and scope of data

Allow designer to understand business processes

Allow designer to develop appropriate relationship participation rules and constraints

Promote creation of an accurate data model

Generally, nouns translate into entities

Verbs translate into relationships among entities

Relationships are bi-directional

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

The Evolution of Data Models

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

The Evolution of Data Models (cont..)

Hierarchical

Network

Relational

Entity relationship

Object oriented (OO)

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

The Hierarchical Model

Developed in the 1960s to manage large amounts of data for complex manufacturing projects

Basic logical structure is represented by an upside-down “tree”

The hierarchical structure contains levels, or segments

Depicts a set of one-to-many (1:*) relationships between a parent and its children segments

Each parent can have many children

each child has only one parent

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

The Hierarchical Model (cont…)

Advantages

Many of the hierarchical data model’s features formed the foundation for current data models

Its database application advantages are replicated, though in a different form, in current database environments

Generated a large installed (mainframe) base, created a pool of programmers who developed numerous tried-and-true business applications

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

Albeit= Bien que , quoique que , though

20/03/2017

The Hierarchical Model (cont..)

Disadvantages

Complex to implement

Difficult to manage

Lacks structural independence

Implementation limitations

Lack of standards

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

The Network Model

Created to

Represent complex data relationships more effectively than the hierarchical model

Improve database performance

Impose a database standard

While the Network model is not used today, the definitions of standard database concepts are still used by modern data models such as:

Schema

Conceptual organization of entire database as viewed by the database administrator

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

The Network Model (cont..)

Subschema

Defines database portion “seen” by the application programs that actually produce the desired information from data contained within the database

Data Management Language (DML)

Defines the environment in which data can be managed and is used to work with the data in the database

Schema Data Definition Language (DDL)

Enables database administrator to define schema components

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

The Network Model (cont..)

Disadvantages

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

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

The Relational Model

Developed by Codd (IBM) in 1970

Considered ingenious but impractical in 1970

Conceptually simple

Computers lacked power to implement the relational model

Today, microcomputers can run sophisticated Relational Database Software called Relational Database Management System (RDBMS)- Ex: Oracle : mainframe relational software

Performs same basic functions provided by hierarchical and network DBMS systems, in addition to a host of other functions

Most important advantage of the RDBMS is its ability to hide the complexities of the relational model from the user

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

The Relational Model (cont..)

Table

Matrix consisting of a series of row/column intersections

Related to each other through sharing a common entity characteristic

Tables, also called relations are related to each other through the sharing of a common field

Relational diagram

Is a representation of relational database’s entities, attributes within those entities, and relationships between those entities

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

The Relational Model (cont..)

Relational Table

Stores a collection of related entities

Resembles a file

Relational table is purely a logical structure

How data are physically stored in the database is of no concern to the user or the designer

This property became the source of a real database revolution

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

The Relational Model (cont..)

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

The Relational Model (continued)

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

The Relational Model (cont..)

Another raison for the database model’s rise to dominance is its powerful and flexible query language

Structured Query Language (SQL) allows the user to specify what must be done without specifying how it must be done

SQL-based relational database application involves 3 parts:

User interface

A set of tables stored in the database

SQL engine

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

The Entity Relationship Model

Widely accepted and adapted graphical tool for data modeling

Introduced by Peter Chen in 1976

It was the graphical representation of entities and their relationships in a database structure.

More recently the class diagram component of the Unified Modeling Language (UML) has been used to produce entity relationship models.

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

The Entity Relationship Model (cont..)

Entity relationship diagram (ERD)

Uses graphic representations to model database components

Entity is mapped to a relational table

Entity instance (or occurrence) is a row in table

Each entity is described by a set of attributes that describe particular characteristics of the entity

Entity set is collection of like entities

Connectivity labels types of relationships (1-1, 1- M, M-M)

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

The Entity Relationship Model (cont..)

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

The Entity Relationship Model (cont..)

Fig 2.4 The basic Crow’s foot ERD

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

Data Models: A Summary

Each new data model capitalized on the shortcomings of previous models

Common characteristics that data models must have in order to be widely accepted:

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 comply with consistency and integrity characteristics of any data model

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

Data Models: A Summary (cont..)

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

Degrees of Data Abstraction

Way of classifying data models

Many processes begin at high level of abstraction and proceed to an ever-increasing level of detail

Designing a usable database follows the same basic process

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

Degrees of Data Abstraction (cont..)

In the early 1970s, the American National Standards Institute (ANSI) Standards Planning and Requirements Committee (SPARC)

Defined a framework for data modeling based on degrees of data abstraction:

External

Conceptual

Internal

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

Degrees of Data Abstraction (cont..)

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

The External Model

End users’ view of the data environment

Requires that the modeler subdivide set of requirements and constraints into functional modules that can be examined within the framework of their external models

Advantages:

Easy to identify specific data required to support each business unit’s operations

Facilitates designer’s job by providing feedback about the model’s adequacy

Creation of external models helps to ensure security constraints in the database design

Simplifies application program development

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

The External Model (cont..)

Fig 2.9 External Models for Tiny College

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

The External Model (cont..)

Fig 2.9 External Models for Tiny College

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

The Conceptual Model

Represents global view of the entire database

Representation of data as viewed by the entire organization

The conceptual is the basis for identification and high-level description of main data objects, avoiding details

Most widely used conceptual model is the entity relationship (ER) model

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

The Conceptual Model (cont..)

Fig 2.10 The Conceptual Model for Tiny College

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

The Conceptual Model (cont..)

First, the CM provides a relatively easily understood macro level view of data environment

Second, the CM is independent of both software and hardware

Does not depend on the DBMS software used to implement the model

Does not depend on the hardware used in the implementation of the model

Changes in either hardware or DBMS software have no effect on the database design at the conceptual level

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

The Internal Model

Is the representation of the database as “seen” by the DBMS

The internal model should map the conceptual model to the DBMS

The internal schema depicts a specific representation of an internal model

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

Fig 2.11 An Internal Model for Tiny College

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

The Physical Model

Operates at lowest level of abstraction, describing the way data are saved on storage media such as disks or tapes

Software and hardware dependent

Requires that database designers have a detailed knowledge of the hardware and software used to implement database design

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

The Physical Model (cont..)

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

Summary

A data model is a (relatively) simple abstraction of a complex real-world data environment

Basic data modeling components are:

Entities

Attributes

Relationships

Constraints

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

Summary (cont..)

Hierarchical model

Depicts a set of one-to-many (1:*) relationships between a parent and its children segments

Network data model

Uses sets to represent 1:* relationships between record types

Relational model

Current database implementation standard

ER model is a popular graphical tool for data modeling that complements the relational model

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

Summary (cont..)

Object is basic modeling structure of object oriented data model

The relational model has adopted many object-oriented extensions to become the extended relational data model (ERDM)

Data modeling requirements are a function of different data views (global vs. local) and level of data abstraction

NoSQL databases are a new generation of databases that do not use the relational model and are geared to support the very specific needs of Big Data organizations

Additional slides are next

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

The Object Oriented Model

Modeled both data and their relationships in a single structure known as an object

Object-oriented data model (OODM) is the basis for the object-oriented database management system (OODBMS)

OODM is said to be a semantic data model

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

The Object Oriented Model (cont..)

Object described by its factual content

Like relational model’s entity

Includes information about relationships between facts within object, and relationships with other objects

Unlike relational model’s entity

Subsequent OODM development allowed an object to also contain all operations

Object becomes basic building block for autonomous structures

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

The Object Oriented Model (cont..)

Object is an abstraction of a real-world entity

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

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

The Object Oriented Model (cont..)

Fig 2.5 A comparison of the OO model and the ER model

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

Other Models

Extended Relational Data Model (ERDM)

Semantic data model developed in response to increasing complexity of applications

DBMS based on the ERDM often described as an object/relational database management system (O/RDBMS)

Primarily geared to business applications

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

Emerging Data Models: Big Data and NoSQL

Big Data refers to a movement to find new and better ways to manage large amounts of Web-generated data and derive business insight from it, while simultaneously providing high performance and scalability at a reasonable cost.

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

Emerging Data Models: Big Data and NoSQL (cont…)

The relational approach does not always match the needs of organizations with Big Data challenges.

It is not always possible to fi t unstructured, social media data into the conventional relational structure of rows and columns.

Adding millions of rows of multi-format (structured and nonstructured) data on a daily basis will

inevitably lead to the need for more storage, processing power, and sophisticated data analysis

tools that may not be available in the relational environment.

The type of high-volume implementations required in the RDBMS environment

for the Big Data problem comes with a hefty price tag for expanding hardware, storage, and software licenses.

Data analysis based on OLAP tools has proven to be very successful in relational environments with highly structured data.

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

Database Models and the Internet

Internet drastically changed role and scope of database market

OODM and ERDM-O/RDM have taken a backseat to development of databases that interface with Internet

Dominance of Web has resulted in growing need to manage unstructured information

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

20/03/2017

NoSQL Databases

NoSQL to refer to a new generation of databases that address the specific challenges of the Big Data era.

They have the following general characteristics:

Not based on the relational model, hence the name NoSQL.

Supports distributed database architectures.

Provides high scalability, high availability, and fault tolerance.

Supports very large amounts of sparse data.

Geared toward performance rather than transaction consistency.

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

NoSQL Databases (cont..)

The key-value data model is based on a structure composed of two data elements: a key and a value, in which every key has a corresponding value or set of values.

The key-value data model is also referred to as the attribute-value or associative data model.

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

NoSQL Databases (cont…)

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

NoSQL Databases (cont..)

The data type of the “value” column is generally a long string to accommodate the variety of actual data types of the values placed in the column.

To add a new entity attribute in the relational model, you need to modify the table definition.

To add a new attribute in the key-value store, you add a row to the key-value store, which is why it is said to be “schema-less.”

NoSQL databases do not store or enforce relationships among entities.

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett

NoSQL Databases (cont..)

NoSQL databases use their own native application programming interface (API) with simple data access commands, such as put, read, and delete.

Indexing and searches can be difficult. Because the “value” column in the key-value data model could contain many different data types, it is often difficult to create indexes on the data. At the same time, searches can become very complex.

Database Principles 2nd Ed., Coronel, Morris, Rob & Crockett