Transcript Fundamentals of Database Systems - Monash University, Victoria

IMS1907 Database Systems
Summer Semester 2004/2005
Lecture 1
Introduction to Database Systems
Fundamentals and Concepts
People
Lecturer
– David Grant
– Phone 9903 1064
– [email protected]
Tutors
– Reagan Low
– Arvind Arcot
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Resources
www.sims.monash.edu.au/subjects/IMS1907/index.html
www.sims.monash.edu.au/resources/assessment.html
Required text book
– Hoffer, J.A., Prescott, M.B. and McFadden, F.R.,
(2002), (7th edn.), Modern Database Management,
Pearson Education Inc., Upper Saddle River, NJ,
USA.
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Unit Structure
1 x 2 hour lecture per day for 13 days
1 x 2 hour laboratory/tutorial per day
– tutorial exercises
– unit test preparation
Two unit tests together worth 20% each
– Microsoft Access, SQL
One final examination, 3 hours, worth 60%
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Inescapable Truths
Lecturers do not really teach you anything, they present you
with toolkits and information
The overheads are a guide to points of discussion - they do
not contain the total wisdom on any given topic
They identify and discuss the topics and issues you need to
consider and understand when using the tools
You learn by your own efforts at reading, comprehending,
discussing and doing – this is a technical subject!
Your assessed outcomes, generally, are directly
proportional to your effort - you make yourself more equal!
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Database Systems Topics
Introduction. database fundamentals and concepts
Data modelling
Relational theory
Normalisation
SQL
Database systems development
Database design and optimisation
Data warehouses, OODBMS, internet DBs
Database systems and organisations - roles of DA, DBA
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What are Database Systems?
Many different types of information systems
– TPS, GIS, MIS, DSS, EIS, KBS, expert, messaging,
HRIS, SIS, enterprise…..
…used IS in many business areas to perform many functions
– banking, airlines, universities, credit cards, finance,
telecommunications, sales, manufacturing, HR
Almost all of these rely on a database in some way
In fact, database systems are at the heart of most
information systems
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Impact of Database Systems
The amount of information being collected and stored is
almost beyond comprehension – and its growing
Stored information is being used for more purposes than
were conceivable ten (or even five) years ago
Databases are used at every level of society
– individuals, small business, national organisations, global
corporations, governments…
They affect many aspects of our everyday lives
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Impact of Database Systems
Databases are used in
– monitoring and improving business operations
– tracking customers and their behaviour
– tracking and despatching emergency service vehicles
– monitoring communications with space vehicles
– making decisions (business and otherwise)
– generating spam
– performing surgical procedures
– many other applications from the mundane to miraculous
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Impact of Database Systems
Critical to business productivity and profitability
Critical to individual life and safety
Instrumental in economic and social stability
Can affect governments
It essential that information is accurate, up-to-date and
consistent
Not always easy when there are so many databases of so
many types storing different versions of similar or the same
information
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A Brief History of Database Systems
3000BC(?)
knotted and coloured string, marks on clay
2000BC(?)
papyrus-based recording
200BC(?)
paper-based technologies
1950
file processing systems
1970
hierarchical DBMS,network DBMS (first
generation DBMS), Codd’s relational
model
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A Brief History of Database Systems
1980
1990
2000+
relational DBMS (second generation
DBMS), SQL
internet, data warehouses, object-oriented
DBMS, distributed databases
more complex data structures, universal
servers, centralised databases, contentaddressable storage, AI, data mining,
mobile technologies, super computers…
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Basic Concepts
Central concepts for understanding database systems
– Database
– Data
– Information
– Data vs Information
– Metadata
– DBMS
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Database
An organised collection of logically related data
Has some inherent meaning
Represents some aspect of the real world (UoD)
Vary in size and complexity (MB  TB)
Designed, built, and populated with data for a specific
purpose and for intended users
Generated and maintained manually or computerised
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Data
Traditionally referred to facts about things and events that
could be recorded and stored (…on computer media)
Referred to as structured data
Data types are numeric, characters, dates
Stored as records in files (older) or more commonly in
tabular form (tables, relations, arrays, spreadsheets, etc)
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Data
Traditional definition does not reflect current reality
– structured data is the not the only type stored
Documents, images, sound, video
Unstructured data or multimedia data
– “…stored representations of objects and events that have
meaning and importance in the users environment.”
Multimedia environments store and display structured and
unstructured data
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Data vs Information
The terms data and information are often used
interchangeably but it is useful to distinguish between them
Information
– “…data that have been processed in such a way that the
knowledge of the person who uses the data is increased.”
– data with a context and other associated useful data
– often summarised or otherwise-processed data that is
presented for interpretation
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Metadata
“…data that describe the properties or characteristics of end
user data and the context of that data.”
Data names, definitions, length/size, allowable values
Data source, storage location, stewardship, usage
Data about data – once removed from the data
Enables users and designers to understand what data
exists, what it means – avoid errors, misinterpretation
Stored in the system catalog
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Database Management System (DBMS)
“…a software system that is used to create, maintain, and
provide controlled access to user databases.”
A general purpose set of software tools that facilitates the
process of defining, constructing and manipulating data in a
database for some specific purpose in a known context
Provides systematic method for creating, updating, storing
and retrieving data in a database
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Database Management System (DBMS)
Data sharing between end users and programmers
Data sharing across multiple applications
Data access control, data integrity enforcement,
concurrency control, restoration
MS Access, MS SQL Server, Oracle, MySQL, Informix, DB2,
Teradata, Ingres, SyBase
Objectivity, Cache, Gemstone, Jasmine, O2, ObjectStore,
POET, Versant
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DBMS vs File Processing Systems
Traditional File Processing systems had disadvantages
– program-data dependence
– data duplication, inconsistency
– integrity problems
– hard to access
– atomicity, concurrency, security problems
– limited data sharing
– lengthy development times
– excessive program maintenance
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DBMS vs File Processing Systems
DBMS provide benefits when compared to traditional File
Processing systems
– program-data independence
– minimal data redundancy - controlled
– improved data consistency
– improved data sharing
– improved access and security controls
– increased productivity of application development
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DBMS vs File Processing Systems
DBMS benefits
– enforcement of standards
– improved data quality
– improved data accessibility and responsiveness
– reduced program maintenance
– improved decision support
– persistent storage for application objects and data
structures
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DBMS vs File Processing Systems
DBMS benefits
– rule-based inferencing and actions
– multiple user interfaces
– multi-user transaction processing
– represent complex data relationships
– enforce integrity constraints
– backup and recovery
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What are Database Systems?
A database system contains
– DBMS
– database
– metadata (repository)
Also in the database system environment are
– application software
– CASE tools
– user interfaces
– users, developers, administrators
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Database Systems
Users/developers
DATABASE
SYSTEM
Application programs/queries
DBMS
Software to process queries/programs
Software to access stored data
Database
Metadata
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Database Systems
Data and database
administrators
System
developers
End users
CASE
tools
User
interfaces
Application
programs
Metadata
DBMS
Database
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Types of Database Systems
Personal Databases
Workgroup Databases
Department Databases
Enterprise Databases
Internet, Intranet, and Extranet Databases
Data warehouses
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Costs and Risks of Database Systems
Need for new, specialised personnel
Installation cost and complexity
Maintenance cost and complexity
Conversion costs from legacy systems
Critical need for explicit backup and recovery
Organisational conflict and change
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Database Systems and Organisations
An organisation’s success or failure can depend on the
accuracy and availability of its information
An expensive pause… (source: Standish Group)
Cost of downtime/minute
@ normal load
Cost of downtime/minute
@ peak load
CRM
$2,200
$2,500
Data Warehouse
$5,800
$6,300
Electronic Commerce
$2,500
$7,800
ERP
$6,400
$7,900
SCM
$4,400
$6,600
Application
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Database Systems and You
What databases have you been in contact with this week?
(directly and indirectly)
What databases are you on that you know about?
What databases do you think you might be on that you don’t
know about?
How important is it that you are on at least some databases?
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Reading for Next Week
Hoffer et al, Chapter 2
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References
Elmasri, R. and Navathe, S.B., (2000), (3rd edn.),
Fundamentals of Database Systems, Addison-Wesley,
Reading, Massachusetts, USA.
Hoffer, J.A., Prescott, M.B. and McFadden, F.R., (2002), (7th
edn.), Modern Database Management, Pearson Education
Inc., Upper Saddle River, NJ, USA.
Murphy, B., (1999), Data Downtime Dilemma, accessed 5th
July 2004 at
http://www.findarticles.com/p/articles/mi_m0SMG/is_3_19/ai
_59329322.
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