Transcript Models - Courses

Lecture 11: Intro to Database Design
SIMS 202:
Information Organization
and Retrieval
Prof. Ray Larson & Prof. Marc Davis
UC Berkeley SIMS
Tuesday and Thursday 10:30 am - 12:00 pm
Fall 2004
http://www.sims.berkeley.edu/academics/courses/is202/f04/
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Lecture Overview
• Review
– Evaluation exercise
•
•
•
•
•
Databases and Database Design
Database Life Cycle
ER Diagrams
Discussion
Next Time/Readings
IS 202 – FALL 2004
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Lecture Overview
• Review
– Evaluation exercise
•
•
•
•
•
Databases and Database Design
Database Life Cycle
ER Diagrams
Discussion
Next Time/Readings
IS 202 – FALL 2004
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What is a Database?
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Files and Databases
• File: A collection of records or documents
dealing with one organization, person,
area or subject (Rowley)
– Manual (paper) files
– Computer files
• Database: A collection of similar records
with relationships between the records
(Rowley)
– Bibliographic, statistical, business data,
images, etc.
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Database
• A Database is a collection of stored
operational data used by the application
systems of some particular enterprise
(C.J. Date)
– Paper “Databases”
• Still contain a large portion of the world’s
knowledge
– File-Based Data Processing Systems
• Early batch processing of (primarily) business data
– Database Management Systems (DBMS)
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Why DBMS?
• History
– 50’s and 60’s all applications were custom
built for particular needs
– File based
– Many similar/duplicative applications dealing
with collections of business data
– Early DBMS were extensions of programming
languages
– 1970 - E.F. Codd and the Relational Model
– 1979 - Ashton-Tate and first Microcomputer
DBMS
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File Based Systems
Application
Delivery
List
Coal
Estimation
Just what
asked for
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File
Toys
Addresses
Naughty
Nice Toys
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From File Systems to DBMS
• Problems with file processing systems
– Inconsistent data
– Inflexibility
– Limited data sharing
– Poor enforcement of standards
– Excessive program maintenance
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DBMS Benefits
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Minimal data redundancy
Consistency of data
Integration of data
Sharing of data
Ease of application development
Uniform security, privacy, and integrity controls
Data accessibility and responsiveness
Data independence
Reduced program maintenance
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Terms and Concepts
• Data independence
– Physical representation and location of data
and the use of that data are separated
• The application doesn’t need to know how or
where the database has stored the data, but just
how to ask for it
• Moving a database from one DBMS to another
should not have a material effect on application
program
• Recoding, adding fields, etc. in the database
should not affect applications
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Database Environment
CASE
Tools
Repository
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User
Interface
DBMS
Application
Programs
Database
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Database Components
DBMS
===============
Design tools
Database
Database contains:
User’s Data
Metadata
Indexes
Application Metadata
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Table Creation
Form Creation
Query Creation
Report Creation
Procedural
language
compiler (4GL)
=============
Run time
Form processor
Query processor
Report Writer
Language Run time
Application
Programs
User
Interface
Applications
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Types of Database Systems
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PC databases
Centralized database
Client/server databases
Distributed databases
Database models
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PC Databases
E.g.:
Access
FoxPro
Dbase
Etc.
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Centralized Databases
Central
Computer
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Client Server Databases
Client
Client
Network
Database
Server
Client
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Distributed Databases
Location C
Location B
computer
computer
computer
Homogeneous
Databases
Location A
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Distributed Databases
Client
Heterogeneous
Or Federated
Databases
Database
Server
Remote
Comp.
Local Network
Comm
Server
Client
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Remote
Comp.
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Terms and Concepts
• A “database application” is an application
program (or set of related programs) that is used
to perform a series of database activities:
– Create
• Add new data to the database
– Read
• Read current data from the database
– Update
• Update or modify current database data
– Delete
• Remove current On behalf of database users
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Terms and Concepts
• Enterprise
– Organization
• Entity
– Person, Place, Thing, Event, Concept...
• Attributes
– Data elements (facts) about some entity
– Also sometimes called fields or items or domains
• Data values
– Instances of a particular attribute for a particular
entity
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Terms and Concepts
• Key
– An attribute or set of attributes used to identify
or locate records in a file
• Primary Key
– An attribute or set of attributes that uniquely
identifies each record in a file
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Terms and Concepts
• Models
– (1) Levels or views of the Database
• Conceptual, logical, physical
– (2) DBMS types
• Relational, Hierarchic, Network, Object-Oriented,
Object-Relational
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Models (1)
Application 1
External
Model
Application 2
Application 3
Application 4
External
Model
External
Model
External
Model
Application 1
Conceptual
requirements
Application 2
Conceptual
requirements
Application 3
Conceptual
requirements
Conceptual
Model
Logical
Model
Internal
Model
Application 4
Conceptual
requirements
More later on this…
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Data Models(2): History
• Hierarchical Model (1960’s and 1970’s)
– Similar to data structures in programming
languages
Books
(id, title)
Authors
(first, last)
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Publisher
Subjects
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Data Models(2): History
• Network Model (1970’s)
– Provides for single entries of data and
navigational “links” through chains of data.
Authors
Subjects
Books
Publishers
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Data Models(2): History
• Relational Model (1980’s)
– Provides a conceptually simple model for data
as relations (typically considered “tables”) with
all data visible
pubid
Book ID
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Title
pubid
Introductio
The history
New stuff ab
Another title
And yet more
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2
4
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1
Author id
1
2
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5
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2
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Book ID
pubname
Harper
Addison
Oxford
Que
Authorid
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Author name
Smith
Wynar
Jones
Duncan
Applegate
Subid
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Subid
Subject
1 cataloging
2 history
3 stuff
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Data Models(2): History
• Object Oriented Data Model (1990’s)
– Encapsulates data and operations as
“Objects”
Books
(id, title)
Authors
(first, last)
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Publisher
Subjects
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Data Models(2): History
• Object-Relational Model (1990’s)
– Combines the well-known properties of the
Relational Model with such OO features as:
• User-defined datatypes
• User-defined functions
• Inheritance and sub-classing
• All of the major enterprise DBMS systems
are now Object-Relational or incorporate
Object-Relational features
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Lecture Overview
• Review
– MediaStreams
•
•
•
•
•
Databases and Database Design
Database Life Cycle
ER Diagrams
Discussion
Next Time/Readings
IS 202 – FALL 2004
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Database System Life Cycle
Physical
Creation
2
Conversion
3
Design
1
Growth,
Change, &
Maintenance
6
Integration
4
Operations
5
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Design
• Determination of the needs of the
organization
• Development of the Conceptual Model of
the database
– Typically using Entity-Relationship
diagramming techniques
• Construction of a Data Dictionary
• Development of the Logical Model
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Physical Creation
• Development of the Physical Model of the
Database
– Data formats and types
– Determination of indexes, etc.
• Load a prototype database and test
• Determine and implement security, privacy
and access controls
• Determine and implement integrity
constraints
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Conversion
• Convert existing data sets and
applications to use the new database
– May need programs, conversion utilities to
convert old data to new formats
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Integration
• Overlaps with Phase 3
• Integration of converted applications and
new applications into the new database
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Operations
• All applications run full-scale
• Privacy, security, access control must be in
place
• Recovery and Backup procedures must be
established and used
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Growth, Change, and Maintenance
• Change is a way of life
– Applications, data requirements, reports, etc.
will all change as new needs and
requirements are found
– The Database and applications and will need
to be modified to meet the needs of changes
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Another View of the Life Cycle
Integration
4
Operations
5
Design
Physical
1
Creation Conversion Growth,
2
Change
3
6
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Lecture Overview
• Review
– MediaStreams
•
•
•
•
•
Databases and Database Design
Database Life Cycle
ER Diagrams
Discussion
Next Time/Readings
IS 202 – FALL 2004
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Database Design Process
Application 1
External
Model
Application 2
Application 3
Application 4
External
Model
External
Model
External
Model
Application 1
Conceptual
requirements
Application 2
Conceptual
requirements
Application 3
Conceptual
requirements
Conceptual
Model
Logical
Model
Internal
Model
Application 4
Conceptual
requirements
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Entity
• An Entity is an object in the real world (or
even imaginary worlds) about which we
want or need to maintain information
– Persons (e.g.: customers in a business,
employees, authors)
– Things (e.g.: purchase orders, meetings,
parts, companies)
Employee
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Attributes
• Attributes are the significant properties or
characteristics of an entity that help identify it
and provide the information needed to
interact with it or use it (this is the Metadata
for the entities)
Birthdate
First
Middle
Last
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Age
Name
Employee
SSN
Projects
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Relationships
• Relationships are the associations
between entities
• They can involve one or more entities and
belong to particular relationship types
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Relationships
Student
Attends
Class
Project
Supplier
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Supplies
project
parts
Part
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Types of Relationships
• Concerned only with cardinality of
relationship
Employee
Employee
Employee
1 Assigned
n
Assigned
1
1
m Assigned n
Truck
Project
Project
Chen ER notation
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Other Notations
Employee
Assigned
Truck
Employee
Assigned
Project
Employee
Assigned
Project
“Crow’s Foot”
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Other Notations
Employee
Assigned
Truck
Employee
Assigned
Project
Employee
Assigned
Project
IDEFIX Notation
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More Complex Relationships
Manager
1/1/1
Employee
1/n/n Evaluation n/n/1
Project
SSN
Date
Project
Employee
4(2-10)
Assigned
1
Manages
Employee
Is Managed By
Project
1
Manages
n
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Weak Entities
• Owe existence entirely to another entity
Part#
Invoice #
Order
Invoice#
Contains
Quantity
Order-line
Rep#
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Supertype and Subtype Entities
Employee
Sales-rep
Is one of
Manages
Clerk
Sold
Other
Invoice
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Many to Many Relationships
SSN
Proj#
Proj#
Hours
Project
Assignment
Is
Assigned
Project
Assigned
Employee
IS 202 – FALL 2004
SSN
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Lecture Overview
• Review
– MediaStreams
•
•
•
•
•
Databases and Database Design
Database Life Cycle
ER Diagrams
Discussion
Next Time/Readings
IS 202 – FALL 2004
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Discussion
• Why use DBMS for web-based system
development?
• Why Not use IR systems?
• Can you use both?
• Other Questions?
IS 202 – FALL 2004
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Lecture Overview
• Review
– MediaStreams
•
•
•
•
•
•
Databases and Database Design
Database Life Cycle
ER Diagrams
Database Design
Discussion
Next Time/Readings
IS 202 – FALL 2004
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Next Time
• Database Design – Normalization and
SQL
• Readings
– Hoffer/McFadden “Logical database Design
and the Relational Model”
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