organizing data and information c h a p t e r
DESCRIPTION
TRANSCRIPT
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Organizing
Data and Information
C H A P T E R
5
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The Hierarchy of Data
DatabaseCollection 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
DatabaseCollection of integrated and related files
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Data Entities, Attributes, and Keys
EntityGeneralized class of people, places, or things for which
data is collected, stored, and maintained
Attribute Characteristic of an entity
Data itemSpecific 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 recordPrimary 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
Entities (records)
Key field Attributes
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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 redundancyImproved data integrityEasier modification and updatingData and program independence
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Advantages of the Database Approach
Better access to data and informationStandardization of data accessA framework for program developmentBetter overall protection of the dataShared 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?
AccessWhat data is to be provided to which users when
appropriate?
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Database Considerations
Logical structureHow is the data to be arranged so that it makes sense to a
given user?
Physical organizationWhere 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 organization’s 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 modelA 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 (1:1)One-to-many (1:N)Many-to-many (N:M)
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[Figure 5.5]
An Entity-Relationship Diagram
An ER diagram for a customer ordering database
Entities
Relationship
Attributes
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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 placedTuple: Each row of a table Attributes: Columns of the tableDomain: Values for attributes or columns
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Relational Models
[Figure 5.8]
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Data Manipulations
SelectingEliminating rows according to certain criteria
ProjectingEliminating columns in a table
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Data Manipulations
Joining Combining two or more tables
LinkingJoining tables that share at least one common data element
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Data Analysis and Normalization
Data analysisEvaluation of data to uncover problems with the content
of a database
Anomalies Problems and irregularities in data
NormalizationRemoving anomalies from a database
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Comparison of Database Models
Hierarchical modelPrimary advantage: processing efficiency
Network modelMore flexible than hierarchical models in terms of
organizing data
Relational database modelEasier to control, more flexible, and more intuitive; by far
the most widely used
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Database Characteristics
AmountDatabase size depends on the number of records or files it
contains
VolatilityA measure of the changes typically required in a given
period of time
ImmediacyA 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 supportHierarchicalNetworkRelational
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Storing and Retrieving Data
Logical access path Application requests data
from the DBMS
Physical access pathDBMS accesses a storage
device to retrieve the data
[Figure 5.14]
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Data Control
Concurrency controlLocks out simultaneous access to a record that is being
updated or used by another program
SchemaThe logical and physical structure of the data and
relationships among the data in the database
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Providing a User View
User viewPortion 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 dictionaryA 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 approachReduced data redundancyIncreased data reliabilityFaster program developmentEasier 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 databaseAllows 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 become
an integral part of most relational database packages
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Selecting a Database Management System
Begins by analyzing database needs and characteristicsPerformanceIntegrationFeaturesThe vendorCost
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Emerging Database Trends
Distributed databasesActual data may be spread across several smaller
databases connected via telecommunications devices
Replicated databaseHolds 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 warehouseBrings 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 miningAutomated 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 databasesStore data in the form of images
Hypertext databasesAllow users to search and manipulate alphanumeric data
in an unstructured way
Hypermedia databasesAllow 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 databaseDevelopment and maintenance of schemas and
subschemasDevelopment and maintenance of the data
dictionaryImplementation of the DBMS
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Aspects of Database Administration
System and user documentation User support and trainingOverall operation of the DBMSTesting and maintaining the DBMSEstablishing 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?