Chapter 2 flashcards HLST 3320

Data modelling refers to the process of

creating a specific data model for a determined problem domain

Data modelling as an _________ , progressive process

Iterative

Data model

Is a simple representation of more complex real-world data structures

A problem domain

Is a clearly defined area within the real-world environment, with well-defined scope and boundaries, that is to be systemically addressed

An implementation-ready data model should contain at least the following components:

* A description of the data structure that will store the end-user data.
* A set of enforceable rules to guarantee the integrity of the data.
* A data manipulation methodology to support the real-world data transformations.

Database designers make use of _________ data-modelling constructs and powerful database design tools that diminish the potential for errors in database modelling

existing

Data models are a ________ tool

Communication

Why are data models important?

Because data is viewed in different ways by different people and you will be unlikely to create a good database without first creating and appropriate data model

A sound data environment requires an **____________________** based on an appropriate data model

overall database blueprint

When a good database blueprint is available, it does not matter that an applications programmer’s **______** of the data is different from that of the manager or the end user

view

Entity

is a person, place, thing, concept, or event about which data will be collected and stored

Attribute

is a characteristic of an entity

Relationship

describes an association among entities

What are the three different types of relationships

* 1:M or 1..\*
* M:N or \**..**
* 1:1 or 1..1

Relationships are

bidirectional

A constraint is

A restriction placed on the data

Why are constraints important?

They help ensure data integrity

Constraints are usually expressed in the form of _____

rules

Example of a constraint

A students GPA must be between 0.0 and 4.0

Business rule

is a brief, precise, and unambiguous description of a policy, procedure, or principle within a specific organization (anything that stores data)

What are business rules used for?

Business rules are used to define entities, attributes, relationships, and constraints

what is the main source of business rules?

The main **sources of business rules** are company managers, policy makers, department managers, and written documentation such as company procedures

Business rules are essential to database design due to the following reasons:

* It helps to standardize the company’s view of data
* It can be a communication tool between users and designers
* It allows the designer to understand the nature, role, and scope of the data
* It allows the designer to understand business processes
* It allows the designer to develop appropriate relationship participation rules and constraints and to create an accurate data model

As a general rule, a noun in a business rule will translate into an ________ in the model, and a verb (active or passive) associating nouns will translate into an ____________ among the entities.

Entity, relationship

What does “a customer generates many invoices” tell you about the organization?

Customer and invoices are nouns therefore they are the entities and generate is the verb which demonstrates the relationship

**Entity names** should be descriptive of

the objects in the business environment and use technology that is familiar to the users

An attribute name should be

descriptive of the data represented

A proper naming convention can help make your model

Self-documenting

What is the first generation of data models?

File system

The second generation of the data models?

Hierarchal and network

The third generation of data models?

Relational

The fourth generation of data models

Object-oriented

What is the next generation of data models?

XML

Why was the hierarchal model developed?

The **hierarchical model** was developed in the 1960s to manage large amounts of data for complex manufacturing projects.

What is a segment?

A segment is the equivalent of a file system’s record type

Within the hierarchy, a higher layer is perceived as the ________ of the segment directly beneath it, which is called the ________.

Parent, child

Why was the network model created?

The **network model** was created to represent complex data relationships more effectively than the hierarchical model, to improve database performance, and to impose a database standard.

How is the network model different from the hierarchal model?

The network model allows a record to have more than one parent

What are the database concepts that emerged with the network model that are still used?

* schema
* Subschema
* Data manipulation language
* Data definition language

Schema

is the conceptual organization of the entire database as viewed by the database administrator.

Subschema

defines the portion of the database “seen” by the application programs that produce the desired information from the data within the database

Data management language (DML)

which defines the environment in which data can be managed and to work with the data in the database.

Data definition language (DDL)

enables the database administrator to define the schema components

What is the foundation of the relational model?

The relational models foundation is a mathematical concept known as relation

What is a relation?

sometimes called a table, is a matrix compose of intersecting rows and columns

Each row in a relation is called a _________.

tuple

Each column represents an

attribute

The relational data model is implemented through a very sophisticated 

Relational database management system (RDBMS)

what is the relational database management system?

The RDBMS performs the same basic functions provided by the hierarchical and network DBMS systems as well as other functions that makes it easier to understand

What is the most important advantage of the RDBMS?

it can hide the complexities of the relational model from the user

What are the three parts of a SQL-based relational database application:

* the end user interface
* A collection of tables
* SQL engine

the end-user interface

the interface allows the end user to interact with the data

A collection of tables

tables “present” the data to the end user in a way that is easy to understand

SQL Engine

the SQL engine executes all queries or data requests

Complex design activities require conceptual ______ to yield successful results

Simplicity

Entity relationship Model

was developed as a graphical tool in which entities and their relationships are pictured

An ER model is made of

* entity
* Attributes
* Relationships

An Entity relationship diagram

uses graphical representations to model database components

\

Chen’s notation

Crows foot Notation

UML Class

Why is the object-oriented data model needed

Increasingly complex real-world problems demonstrated a need for a data model that more closely represented the real world.

In the **object-oriented data model (OODM)**, both data and its relationship are contained in a single structure known as an

Object

The OODM is said to be a **semantic data model** because 

Semantic indicates meaning

The object oriented data model is based on the following components:

* object
* Attributes
* Class
* Class hierarchy
* Inheritance

An object in an OODM is an

abstraction of a real-world entity

Attributes in an OODM describes

the properties of an object

A class in an OODM is

a collection of similar objects with shared structure and behaviour

What does a classes method represent in an OODM?

A class’s **method** represents a real-world action such as finding a selected PERSON’s name, changing a PERSON’s name, or printing a PERSON’s address

What is a class hierarchy

The **class hierarchy** resembles an upside-down tree where each class has only one parent

What is the inheritance?

**Inheritance** is the ability of an object within the class hierarchy to inherit the attributes and methods of the classes above it

Object-oriented data models are typically depicted using **__________________** class diagrams

Unified Modelling language (UML)

What is the UML?

is a language based on OO concepts that describes a set of diagrams and symbols that can be used to graphically model a system.

What are UML class diagrams?

UML class diagrams are used to represent data and their relationships within the larger UML object-oriented system’s modeling language

The **extended relational data model (ERDM)** adds many of the OO model’s features within the ________ relational database structure

simpler

A DBMS based on the ERDM is often described as an

object/relational database management system (O/R DBMS)

What is the Extensible Markup Language (XML)

has emerged as a standard for the efficient and effective exchange of structured, semistructured, and unstructured data

Why is the OR DBMS successful?

The success of the O/R DBMSs can be attributed to the model’s conceptual simplicity, data integrity, easy-to-use query language, high transaction performance, high availability, security, scalability, and expandability

Internet of things

is a web of Internet-connected devices exchanging and collecting data

What is big data

refers to a movement to find new and better ways to manage large amounts of web- and sensor-generated data and derive business insight from it

A basic characteristic of Big Data databases can be described

The 3 V’s, volume, velocity, variety

what are some of the most frequently used big data technologies?

* Hadoop
* Hadoop distributed file system (HDFS)
* Mapreduce
* NoSQL

What is Hadoop?

is a Java-based, open-source, high-speed, fault-tolerant distributed storage and computational framework

What is Hadoop distributed file system

is a highly distributed, fault-tolerant file storage system designed to manage large amounts of data at high speeds

What is MapReduce?

is an open-source application programming interface (API) that provides fast data analytics services

What is NoSQL?

is a large-scale distributed database system that stores structured and unstructured data in efficient ways

What are the general characteristics of NoSQL databases

* They are not based on the relational model and SQL
* They support highly distributed database architectures
* They provide high scalability, high availability, and fault tolerance
* They support very large amounts of sparse data
* They are geared toward performance rather than transaction consistency

What did the American National Standards Institute (ANSI) Standards Planning and Requirements Committee (SPARC) do?

defined a framework for data modeling based on degrees of data abstraction

What are the 3 levels of data abstraction?

* external, conceptual, and internal

What is the external model?

is the end users’ view of the data environment

What does end user mean?

The term end users refers to people who use the application programs to manipulate the data and generate information

What is an external schema?

an external schema is a specific representation of an external view

What are the important advantages of the use of external views that represent subsets of the database?

* It is easy to identify specific data required to support each business unit
* It makes the designer’s job easy by providing feedback about the model’s adequacy
* It helps to ensure security constraints in the database design
* It makes application program development much simpler

What does the conceptual model represent?

The **conceptual model** represents a global view of the entire database by the entire organization

What is the conceptual schema the basis for?

it is the basis for the identification and high-level description of the main data objects

What is the most widely used conceptual model?

the ER model

What is the conceptual model independent of?

it is independent of both software and hardware

What is software independence?

means that the model does not depend on the DBMS software used to implement the model

What is hardware independence?

means that the model does not depend on the hardware used in the implementation of the model. 

What are the advantages of the conceptual model?

* It provides a bird’s-eye view of the data environment that is easy to understand
* The conceptual model is independent of both software and hardware