Post on 12-Jan-2016
1Chapter 1
2Chapter 1
Database Application System & Database Application System & Database ManagementDatabase Management
Definitions Disadvantages of File Processing Database Management System Advantages of the Database Approach Three-Level Database Architecture Program-Data Independence Data and Metadata Data Dictionary Evolution of Database Systems
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DefinitionsDefinitions
– Data: Meaningful facts, text, graphics, images, sound,
video segments.
Data in Context
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DefinitionsDefinitions
– Database: An organized collection of logically related data.
– Information: Data processed to be useful in decision making.
– Metadata: Data that describes data.
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Disadvantages of Disadvantages of File Processing SystemsFile Processing Systems
Program-Data Dependence– All programs maintain metadata for each file they use
Data Redundancy (Duplication of data)– Different systems/programs have separate copies of the same data
Limited Data Sharing– No centralized control of data
Lengthy Development Times– Programmers must design their own file formats
Excessive Program Maintenance– 80% of of information systems budget
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Database Management Database Management SystemSystem
– A DBMS is a data storage and retrieval system which permits data to be stored
non-redundantly while making it appear to the user as if the data is well-integrated.
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Database Management Database Management SystemSystem
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Advantages of the Database Advantages of the Database ApproachApproach
a) Program-Data Independence: The separation of data descriptions (metadata) from
the application programs that use the data is called data independence. This property of database systems allows an organization's data to change and evolve (within limits) without changing the application programs that process the data.
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Advantages of the Database Advantages of the Database ApproachApproach
Problems with Data Dependency Each application programmer must maintain their
own data. Each application program needs to include code
for the metadata of each file. Each application program must have its own
processing routines for reading, inserting, updating and deleting data.
Lack of coordination and central control Non-standard file formats
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Advantages of the Database Advantages of the Database ApproachApproach
b) Minimal Data Redundancy : The design goal with the database approach is that
previously separate (and redundant) data files are integrated into a single, logical structure. Each primary fact is recorded (ideally) in only one place in the database. For example, the fact that the product with Product_ID 3 is an oak computer desk with a unit price of $375.00 is recorded in one place in the Product table
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Advantages of the Database Advantages of the Database ApproachApproach
c) Improved Data Consistency : By eliminating (or controlling) data redundancy, we
greatly reduce the opportunities for inconsistency. For example, if a customer address is stored only once, we cannot have disagreement on the stored values.
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Advantages of the Database Advantages of the Database ApproachApproach
d) Improved Data Sharing : A database is designed as a shared corporate
resource. Authorized users are granted permission to use the database, and each user (or group users) is provided one or more user views to facilitate this use.
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Advantages of the Database Advantages of the Database ApproachApproach
e) Increased Productivity of Application Development :
A major of the database approach is that it greatly reduces the cost and time for developing new business applications.
f) Enforcement of Standards When the database approach is implemented with full
management support, the database administration function should be granted single-point authority and responsibility for establishing and enforcing data standards
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Advantages of the Database Advantages of the Database ApproachApproach
g) Improved Data Quality : The database approach provides a number of tools
and processes to improve data quality
h) Improved Data Accessibility and Responsiveness
With a relational database, end users without programming experience can often retrieve and display data, even when it crosses traditional departmental boundaries
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Advantages of the Database Advantages of the Database ApproachApproach
i) Reduced Program Maintenance : Stored data must be changed frequently for a variety
of reasons: new data item types are added, data formats are changed, and so on. In a database environment, data are more independent of the application programs that use them. Within limits, we can change either the data or the application programs that use the data without necessitating a change in the other factor. As a result, program maintenance can be significantly reduced in a modern database environment
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Database ArchitectureDatabase Architecture
generalized framework proposed by ANSI/SPARC Committee
3 levels– External– Conceptual– Internal
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3 Levels in Architecture of a 3 Levels in Architecture of a DBMSDBMS
External level– consists of the user (group) views of the database– each user will have its own view of the database
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External level of DBMSExternal level of DBMS
Concern with the way the data is viewed by individual user- application programmer or on-line terminal user
for application programmer- language such as VB, VC, powerbuilder, COBOL
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3 Levels in Architecture of a 3 Levels in Architecture of a DBMSDBMS
Conceptual level– involves analysis of users’ information needs
and definition of data items needed to meet them
– the result of the conceptual design is the conceptual schema, a single, logical description of all data elements and their relationships
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Conceptual level of DBMSConceptual level of DBMS
Level of indirection between internal and external level a representation of the entire information content of the
database consists of multiple occurrences of multiple types of
conceptual record
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3 Levels in Architecture of DBMS3 Levels in Architecture of DBMS
Internal Level– provides the physical view of the database- the disk
drives, physical address, indexes, pointers and so on.– This level is the responsibility of physical database
designers.
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Internal level of DBMSInternal level of DBMS
Concern with the way the data is physically stored low-level representation of the entire database internal record is same as stored record
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3 Levels in Architecture of a 3 Levels in Architecture of a DBMSDBMS
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Program-Data Program-Data IndependenceIndependence
– Separation of data description from application program
– Data description are stored in central location called repository
– Allows organization’s data to change without changing the application program
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Data and Meta-dataData and Meta-data
Data– meaningful facts, text, graphics, images, sound etc.
Metadata– describe the properties / characteristics of other data.
include data definitions and data structures. Example on Class Roster, the metadata show
– data item name,
– data type, length,
– minimum and maximum allowable values
– description of each item
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Data Item Value----------------------------------- -----------------------
Name Type Length Min Max Description
Course Alphanumeric 30 Course ID and name
Section Integer 1 1 9 Section number
Semester Alphanumeric 10 Semester and year
Name Alphanumeric 30 Student name
ID Integer 9 Student ID (SSN)
Major Alphanumeric 4 Student major
GPA Decimal 3 0.0 4.0 Student grade point average
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Data DictionaryData Dictionary
– A repository of information about a database which documents data elements of a database.
– An integral part of relational DBMSs is the data dictionary, which stores metadata, or information about the database, including attribute names and definitions for each table in the database.
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Components of the Components of the Database EnvironmentDatabase Environment
CASE Tools – computer-aided software engineering Repository – centralized storehouse of metadata Database Management System (DBMS) – software for managing
the database Database – storehouse of the data Application Programs – software using the data User Interface – text and graphical displays to users Data Administrators – personnel responsible for maintaining the
database System Developers – personnel responsible for designing databases
and software End Users – people who use the applications and databases
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Figure 1-10 Components of the database environment
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Evolution of DB SystemsEvolution of DB Systems
Flat files - 1960s - 1980s Hierarchical – 1970s - 1990s Network – 1970s - 1990s Relational – 1980s - present Object-oriented – 1990s - present Object-relational – 1990s - present Data warehousing – 1980s - present Web-enabled – 1990s - present