Transcript - Courses - University of California, Berkeley

Fourth Generation Languages
(4GLs)
University of California, Berkeley
School of Information Management and
Systems
SIMS 257: Database Management
October 24, 2000
Database Management -- R. Larson
Announcements
• Setting up ORACLE access
– Oracle 8i WebDB and is ready for use…
ALMOST
– We have set up accounts for SIMS and NonSIMS students using your login names.
October 24, 2000
Database Management -- R. Larson
Today
• More on ORACLE
• Fourth Generation Languages
• Use of 4GLs in application development
October 24, 2000
Database Management -- R. Larson
Fourth Generation Languages
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1st Generation -- Machine Language
2nd Generation -- Assembly Languages
3rd Generation -- High-Level Languages
4th Generation -- Non-Procedural Languages
5th Generation -- ?? Knowledge-based ??
Natural Language ??
• Where do Object-Oriented Languages fit??
October 24, 2000
Database Management -- R. Larson
Chauffeurs
• In the early days of the US car industry,
production volumes were growing fast, and a wellknown sociologist was asked to predict the total
number of automobiles that would ever be
manufactured. After a great deal of study, the
sociologist reported that no more than 2 million
would be manufactured in the life cycle of the car.
If the car lasted ten years on average, the
maximum annual production would never exceed
200,000. This conclusion was based on the muchresearched figure that no more than 2 million
people would be willing to serve as chauffeurs.
From James Martin - Fourth Generation Languages
October 24, 2000
Database Management -- R. Larson
Fourth Generation Languages
• In the database environment these are used for creation of
database applications
• To speed up the application building process
• To make applications easy and quick to change
• To minimize debugging problems
• To generate bug-free code from high-level expressions of
requirement
• To make languages user-friendly so that “end-users” can
solve their own problems and put computers to work.
October 24, 2000
Database Management -- R. Larson
Basic Principles of 4GLs
• The Principle of Minimum Work
• The Principle of Minimum Skill
• The Principle of avoiding alien syntax and
mnemonics
• The Principle of Minimum Time
• The Principle of Minimum errors
• The Principle of Minumum Maintenance
• The Principle of Maximum Results
From James Martin - Fourth Generation Languages
October 24, 2000
Database Management -- R. Larson
Properties of 4GLs
• User Friendly
• A nonprofessional programmer can obtain
results with it
• It employs the database management system
directly
• Programs for most applications can be
created with 10 times fewer instructions
than in a Third Generation Language
October 24, 2000
Database Management -- R. Larson
More Properties of 4GLs
• Non procedural code is used wherever
possible
• It make intelligent default assumptions about
what the user wants wherever possible
• It is designed for online operation
• It enforces or encourages structured code
• It makes it easy to understand and maintain
another person’s code
October 24, 2000
Database Management -- R. Larson
More Properties of 4GLs
• Non-DP users can learn a subset of the
language in a short course
• It is designed for easy debugging
• Prototypes can be created and modified
quickly
• Results can be obtained in an order of
magnitude less time than with a 3GL for
most applications
October 24, 2000
Database Management -- R. Larson
Selection Criteria for 4GLs
• Is it intended for routine computing of ad
hoc decision making
• Is it intended for end users or DP
professionals? (many 4GLs are appropriate
for both)
• Does it require the skills of a programmer,
or can an analyst who does not program in a
3GL use it.
October 24, 2000
Database Management -- R. Larson
Selection Criteria for 4GLs
• Which of the following features does it provide?
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Simple queries
Simple queries and updates
Complex queries
Complex queries and updates
The ability to create a database quickly
Intelligent database operations, where the change of one
value in the database causes other operations to occur
automatically, such as validity checks, cross references, and
the updating of related values.
October 24, 2000
Database Management -- R. Larson
Selection Criteria for 4GLs
• Which of the following features does it provide?(cont)
– Generation of data-entry screens for key-entry operators
(with validity checks)
– Generation of data-update screens for key-entry operators
(with validity checks)
– A procedural language giving full programming capability
– Graphics techniques for application design
– Spreadsheet manipulation
– Multidimensional matrix manipulation
– Report generation
– Graphics generation
October 24, 2000
Database Management -- R. Larson
Selection Criteria for 4GLs
• Which of the following features does it provide?(cont)
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Graphics manipulation
Decision support for what-if questions
Mathematical analysis tools
Financial analysis tools
Other decision-support tools
Text manipulation
Electronic Mailbox
• Is it on-line or off-line?
• Does it run on mainframes, minicomputers or personal
computers?
• Can it access mainframe or remote databases
• Is it genuinely easy to use
• Can results be obtained with it very quickly?
October 24, 2000
Database Management -- R. Larson
Components of a 4GL for
building
routine
applications
Application
Parameters
Interpreter
October 24, 2000
Data
Specification
Report
Specification
Screen
Specification
Rules
Specification
Procedural
facility
Feedback
Testing
tools/debugger
Optimizing
compiler
Database Management -- R. Larson
5GLs -- Natural Language
• Possibilities
• Problems
October 24, 2000
Database Management -- R. Larson
Natural Language
• Advantages of using NL
– It encourages untrained users to start
– It encourages upper-management use of
computers
– It reduces the time taken learning complex
syntax
– It lessens the frustration, bewilderment and
anger caused by BAD COMMAND responses
– It is likely to extend greatly the usage of
computers
James Martin, Fourth Generation Languages, 1985
October 24, 2000
Database Management -- R. Larson
Natural Language
Disadvantages of using NL
• It lacks precision
• It is not good for
expressing precise and
complex logic
• It is not good for
expressing neat
structures
• It encourages semantic
overshoot
Appropriate response to the
disadvantage
• It should be combined
with other dialogue
contructs that aid in
the representation of
precise logic and
structures
James Martin, Fourth Generation Languages, 1985
October 24, 2000
Database Management -- R. Larson
Natural Language
Disadvantages of using NL
• It takes substantial
time to key in
sentences
• Ambiguities are
possible
• Substantial
is needed
October 24, 2000
Appropriate response to the
disadvantage
• Sentences and words can
be abbreviated
• Speech input as well as
typed input will be used
• The computer should
detect and resolve
ambiguities
• The processing should be on PC
processing
workstations. Processing is
dropping rapidly in cost.
James Martin, Fourth Generation Languages, 1985
Database Management -- R. Larson
Next Time
• Application development for the Web
environment
– Introduction to Cold Fusion
• Oracle Setup and queries
October 24, 2000
Database Management -- R. Larson