Organizing

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• Organizing
• Data and Information

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The Hierarchy of Data

• Database
• Collection of data organized to meet users
  needs
• Database management system (DBMS)
• Software consisting of a group of programs that
  manipulate the database and provide an interface
  between the database and the application programs

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The Hierarchy of Data

• Data is generally organized in a hierarchy that
  begins with the smallest piece of data (a bit)
  and progresses through thehierarchy to a
  database.

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The Hierarchy of Data

• Character
• Basic building block of information, represented
  by a byte (0,1)
• Field
• A name, number, or combination of characters that
  describes an aspect of a business activity

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The Hierarchy of Data

• Record
• Collection of related fields
• File
• Collection of related records
• Database
• Collection of integrated and related files

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Data Entities, Attributes, and Keys

• Entity
• Generalized class of people, places, or things
  for which data is collected, stored, and
  maintained
• Attribute
• Characteristic of an entity
• Data item
• Specific value of an attribute

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Data Entities,Attributes, and Keys

• Key
• A field or set of fields in a record that is used
  to identify the record
• Primary key
• A field or set of fields that uniquely identifies
  the record
• Secondary key
• A field in a record that does not uniquely
  identify the record

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Keys and Attributes
Key field
Attributes
Entities (records)
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The Traditional Approachto Data Management
Figure 5.3
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Flaws in the Traditional Approach

• Data redundancy
• Duplication of data in separate files
• Data integrity
• The degree to which the data in any one file is
  accurate
• Program-data dependence
• Potential for incompatible programs and data
  between applications

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The Database Approach to Data Management

• Data management in which a pool of related data
  is shared by multiple application programs
• Rather than having separate data files, each
  application uses a collection of data that are
  either joined or related in the database.

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The Database Approach to Data Management
Figure 5.4
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Advantages of theDatabase Approach

• Improved strategic use of corporate data
• Reduced data redundancy
• Improved data integrity
• Easier modification and updating
• Data and program independence

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Advantages of the Database Approach

• Better access to data and information
• Standardization of data access
• A framework for program development
• Better overall protection of the data
• Shared data and information resources

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Disadvantages of the Database Approach

• Relatively high cost of purchasing and operating
  a DBMS in a mainframe operating environment
• Specialized staff
• Increased vulnerability

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Database Considerations

• Content
• What data is to be collected at what cost?
• Access
• What data is to be provided to which users when
  appropriate?

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Database Considerations

• Logical structure
• How is the data to be arranged so that it makes
  sense to a given user?
• Physical organization
• Where is the data to be physically located?

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Types of Database Design

• Logical design
• An abstract model of how the database should be
  structured and arranged to meet an organizations
  information needs
• Physical design
• A model of how the data will be organized and
  located within the database

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Data Modeling and Entity-Relationship Diagrams

• Data model
• A map or diagram of entities and their
  relationships
• Enterprise data modeling
• Data modeling done at the level of the entire
  organization

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Entity-Relationship(ER) Diagrams

• Diagrams that use basic graphical diagrams to
  show the organization of and relationships
  between data
• Relationships include
• One-to-one (11)
• One-to-many (1N)
• Many-to-many (NM)

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An Entity-Relationship Diagram
Figure 5.5
Entities
Relationship
An ER diagram for a customer ordering database
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Database Models

• Hierarchical (tree) models
• Network models
• Relational models

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Hierarchical Database Model

• A model in which the data is organized in
  atop-down or inverted tree-like structure
• Figure 5.6

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Network Models

• An extension of the hierarchical model,in which
  a member may have many owners
• Figure 5.7

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Relational Models

• Data organized in tabular format (rows and
  columns)
• Relations Two-dimensional tables into which
  data elements are placed
• Tuple Each row of a table
• Attributes Columns of the table
• Domain Values for attributes or columns

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Relational Models
Figure 5.8
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Data Manipulations

• Selecting
• Eliminating rows according to certain criteria
• Projecting
• Eliminating columns in a table

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Data Manipulations

• Joining
• Combining two or more tables
• Linking
• Joining tables that share at least one common
  data element

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Data Analysis and Normalization

• Data analysis
• Evaluation of data to uncover problems with the
  content of a database
• Anomalies
• Problems and irregularities in data
• Normalization
• Removing anomalies from a database

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Comparison of Database Models

• Hierarchical model
• Primary advantage processing efficiency
• Network model
• More flexible than hierarchical models in terms
  of organizing data
• Relational database model
• Easier to control, more flexible, and more
  intuitive by far the most widely used

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Database Characteristics

• Amount
• Database size depends on the number of records or
  files it contains
• Volatility
• A measure of the changes typically required in a
  given period of time
• Immediacy
• A measure of how rapidly changes must be made to
  data

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Database Management Systems

• Group of programs used as an interface between a
  database and application programs or a database
  and the user
• Classified by the type of database model they
  support
• Hierarchical
• Network
• Relational

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Storing and Retrieving Data

• Logical access path
• Application requests data from the DBMS
• Physical access path
• DBMS accesses a storage device to retrieve the
  data

• Figure 5.14

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Data Control

• Concurrency control
• Locks out simultaneous access to a record that is
  being updated or used by another program
• Schema
• The logical and physical structure of the data
  and relationships among the data in the database

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Providing a User View

• User view
• Portion of the database a user can access
• Subschema
• A file that contains a description of a subset of
  the database and identifies which users can
  perform modification on the data items in that
  subset
• Developed to create different views

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The Use of Schemas and Subschemas
Figure 5.15
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Creating and Modifyingthe Database

• Data definition language (DDL)
• Collection of instructions and commands used to
  define and describe data and data relationships
  in a specific database

• Figure 5.16

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Creating and Modifyingthe Database

• Data dictionary
• A detailed description of all data used in the
  database

Figure 5.17
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Data Dictionary

• Provides a standard definition of terms and data
  elements
• Assists programmers in designing and writing
  programs
• Simplifies database modifications

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Data Dictionary

• Helps achieve advantages of the database approach
• Reduced data redundancy
• Increased data reliability
• Faster program development
• Easier modification of data and information

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Manipulating Data and Generating Reports

• Data Manipulation Language (DML)
• Contains the commands used to manipulate the
  database
• Allows managers and other database users to
  access, modify, and make queries about data
  contained in the database to generate reports

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Structured Query Language (SQL)
A standardized data manipulation language that
has becomean integral part of most relational
database packages
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Selecting a Database Management System

• Begins by analyzing database needs and
  characteristics
• Performance
• Integration
• Features
• The vendor
• Cost

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Emerging Database Trends

• Distributed databases
• Actual data may be spread across several smaller
  databases connected via telecommunications
  devices
• Replicated database
• Holds a duplicate set of frequently used data

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Distributed Database
HCIA p223
HCIA, Inc. uses a distributed database to
provideup-to-date information to their customers.
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Data Warehouse

• A relational database management system designed
  specifically to support management decision
  making

• Figure 5.21

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Data Warehouse

• Data mart
• Subset of a data warehouse
• Brings the data warehouse concept to small and
  medium-size businesses
• On-line analytical processing (OLAP)
• Consists of programs used to store and deliver
  data warehouse information
• Data mining
• Automated discovery of patterns and relationships
  in a data warehouse

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Open Database Connectivity (ODBC)

• Standards that help ensure that specific software
  can be used with any ODBC-compliant database

• Figure 5.22

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Object-Oriented Databases

• Databases that store data as objects, which
  contain both the data and the processing
  instructions needed to complete the database
  transaction
• Table 5.6

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Image, Hypertext, and Hypermedia Databases

• Image databases
• Store data in the form of images
• Hypertext databases
• Allow users to search and manipulate alphanumeric
  data in an unstructured way
• Hypermedia databases
• Allow businesses to search and manipulate
  multimedia forms of data

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Spatial Data Technology

• Involves the use of an object-relational
  database
• Stores and accesses data according to the
  locations it describes
• Permits spatial queries and analysis

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Aspects of Database Administration

• Overall design and coordination of the database
• Development and maintenance of schemas and
  subschemas
• Development and maintenance of the data
  dictionary
• Implementation of the DBMS

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Aspects of Database Administration

• System and user documentation
• User support and training
• Overall operation of the DBMS
• Testing and maintaining the DBMS
• Establishing emergency or failure-recovery
  procedures

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Database Use, Policies, and Security

• What data should users have direct access to?
• Under what circumstances can data be transferred
  from a PC or small computer system to the large
  mainframe system (uploading)?

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Database Use, Policies, and Security

• Under what circumstances can data be transferred
  from a mainframe system to PCs or small computer
  system (downloading)?
• What procedures are needed to guarantee proper
  database use?