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Fourth Generation Languages and
OR extensions to SQL
University of California, Berkeley
School of Information Management
and Systems
SIMS 257: Database Management
IS 257 - Fall 2002
2002.10.31- SLIDE 1
Lecture Outline
• Review
– PHP (a bit more is working now)…
• Fourth Generation Languages
• Object-Relational Extensions to SQL
IS 257 - Fall 2002
2002.10.31- SLIDE 2
PHP
• PHP is an Open Source Software project
with many programmers working on the
code.
– Commonly paired with MySQL, another OSS
project
– Free
– Both Windows and Unix support
• Estimated that more than 250,000 web
sites use PHP as an Apache Module.
IS 257 - Fall 2002
2002.10.31- SLIDE 3
PHP Syntax
• Similar to ASP
<HTML><BODY>
<?php
$myvar = “Hello World”;
echo $myvar ;
?>
</BODY></HTML>
• Includes most programming structures (Loops,
functions, Arrays, etc.)
• Loads HTML form variables so that they are
addressable by name
IS 257 - Fall 2002
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Combined with MySQL
• DBMS interface appears as a set of
functions:
<HTML><BODY>
<?php
$db = mysql_connect(“localhost”, “root”);
mysql_select_db(“mydb”,$db);
$result = mysql_query(“SELECT * FROM employees”, $db);
printf(“First Name: %s <br>\n”, mysql_result($result, 0 “first”);
printf(“Last Name: %s <br>\n”, mysql_result($result, 0 “last”);
?></BODY></HTML>
IS 257 - Fall 2002
2002.10.31- SLIDE 5
Examples with Diveshop
IS 257 - Fall 2002
2002.10.31- SLIDE 6
Fourth Generation Languages
•
•
•
•
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??
IS 257 - Fall 2002
2002.10.31- SLIDE 7
Chauffeurs
• In the early days of the US car industry,
production volumes were growing fast, and a
well-known 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 much-researched figure that no more than 2
million people would be willing to serve as
chauffeurs.
From James Martin - Fourth Generation Languages
IS 257 - Fall 2002
2002.10.31- SLIDE 8
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 “endusers” can solve their own problems and put
computers to work.
IS 257 - Fall 2002
2002.10.31- SLIDE 9
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
IS 257 - Fall 2002
2002.10.31- SLIDE 10
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
IS 257 - Fall 2002
2002.10.31- SLIDE 11
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
IS 257 - Fall 2002
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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
IS 257 - Fall 2002
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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.
IS 257 - Fall 2002
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Selection Criteria for 4GLs
• Which of the following features does it provide?
–
–
–
–
–
–
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.
IS 257 - Fall 2002
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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
IS 257 - Fall 2002
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Selection Criteria for 4GLs
• Which of the following features does it provide?(cont)
–
–
–
–
–
–
–
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?
IS 257 - Fall 2002
2002.10.31- SLIDE 17
Components of a 4GL
Application
Parameters
Interpreter
IS 257 - Fall 2002
for building routine applications…
Data
Specification
Report
Specification
Screen
Specification
Rules
Specification
Procedural
facility
Feedback
Testing
tools/debugger
Optimizing
compiler
2002.10.31- SLIDE 18
5GLs -- Natural Language
• Possibilities
• Problems
IS 257 - Fall 2002
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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
IS 257 - Fall 2002
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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
IS 257 - Fall 2002
2002.10.31- SLIDE 21
Natural Language
Disadvantages of using NL
• It takes substantial
time to key in
sentences
• Ambiguities are
possible
• Substantial
processing is needed
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 workstations.
Processing is dropping
rapidly in cost.
James Martin, Fourth Generation Languages, 1985
IS 257 - Fall 2002
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Assumptions and Issues
• Why 4GLs?
– Are they still appropriate?
– Are they still useful?
• Is Cold Fusion a 4GL?
• What about PHP?
• Who needs them?
IS 257 - Fall 2002
2002.10.31- SLIDE 23
Object Relational Databases
• Background
• Object Definitions
– inheritance
• User-defined datatypes
• User-defined functions
IS 257 - Fall 2002
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Object Relational Databases
• Began with UniSQL/X unified objectoriented and relational system
• Some systems (like OpenODB from HP)
were Object systems built on top of
Relational databases.
• Miro/Montage/Illustra built on Postgres.
• Informix Buys Illustra. (DataBlades)
• Oracle Hires away Informix Programmers.
(Cartridges)
IS 257 - Fall 2002
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Object Relational Data Model
• Class, instance, attribute, method, and
integrity constraints
• OID per instance
• Encapsulation
• Multiple inheritance hierarchy of classes
• Class references via OID object
references
• Set-Valued attributes
• Abstract Data Types
IS 257 - Fall 2002
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Object Relational Extended SQL (Illustra)
• CREATE TABLE tablename {OF TYPE
Typename}|{OF NEW TYPE typename}
(attr1 type1, attr2 type2,…,attrn typen)
{UNDER parent_table_name};
• CREATE TYPE typename (attribute_name
type_desc, attribute2 type2, …, attrn
typen);
• CREATE FUNCTION functionname
(type_name, type_name) RETURNS
type_name AS sql_statement
IS 257 - Fall 2002
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Object-Relational SQL in ORACLE
• CREATE (OR REPLACE) TYPE typename
AS OBJECT (attr_name, attr_type, …);
• CREATE TABLE OF typename;
IS 257 - Fall 2002
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Example
• CREATE TYPE ANIMAL_TY AS OBJECT
(Breed VARCHAR2(25), Name
VARCHAR2(25), Birthdate DATE);
• Creates a new type
• CREATE TABLE Animal of Animal_ty;
• Creates “Object Table”
IS 257 - Fall 2002
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Constructor Functions
• INSERT INTO Animal values
(ANIMAL_TY(‘Mule’, ‘Frances’,
TO_DATE(‘01-APR-1997’, ‘DD-MMYYYY’)));
• Insert a new ANIMAL_TY object into the
table
IS 257 - Fall 2002
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Selecting from an Object Table
• Just use the columns in the object…
• SELECT Name from Animal;
IS 257 - Fall 2002
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More Complex Objects
• CREATE TYPE Address_TY as object (Street
VARCHAR2(50), City VARCHAR2(25), State
CHAR(2), zip NUMBER);
• CREATE TYPE Person_TY as object (Name
VARCHAR2(25), Address ADDRESS_TY);
• CREATE TABLE CUSTOMER (Customer_ID
NUMBER, Person PERSON_TY);
IS 257 - Fall 2002
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What Does the Table Look like?
•
•
•
•
•
DESCRIBE CUSTOMER;
NAME
TYPE
----------------------------------------------------CUSTOMER_ID
NUMBER
PERSON
NAMED TYPE
IS 257 - Fall 2002
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Inserting
• INSERT INTO CUSTOMER VALUES (1,
PERSON_TY(‘John Smith’,
ADDRESS_TY(‘57 Mt Pleasant St.’, ‘Finn’,
‘NH’, 111111)));
IS 257 - Fall 2002
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Selecting from Abstract Datatypes
• SELECT Customer_ID from CUSTOMER;
• SELECT * from CUSTOMER;
CUSTOMER_ID PERSON(NAME, ADDRESS(STREET, CITY, STATE ZIP))
--------------------------------------------------------------------------------------------------1
PERSON_TY(‘JOHN SMITH’, ADDRESS_TY(‘57...
IS 257 - Fall 2002
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Selecting from Abstract Datatypes
• SELECT Customer_id, person.name from
Customer;
• SELECT Customer_id,
person.address.street from Customer;
IS 257 - Fall 2002
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Updating
• UPDATE Customer SET
person.address.city = ‘HART’ where
person.address.city = ‘Briant’;
IS 257 - Fall 2002
2002.10.31- SLIDE 37
Functions
• CREATE [OR REPLACE] FUNCTION
funcname (argname [IN | OUT | IN OUT]
datatype …) RETURN datatype (IS | AS)
{block | external body}
IS 257 - Fall 2002
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Example
Create Function BALANCE_CHECK
(Person_name IN Varchar2) RETURN NUMBER
is BALANCE NUMBER(10,2) BEGIN
SELECT sum(decode(Action, ‘BOUGHT’,
Amount, 0)) - sum(decode(Action, ‘SOLD’,
amount, 0)) INTO BALANCE FROM LEDGER
where Person = PERSON_NAME;
RETURN BALANCE;
END;
IS 257 - Fall 2002
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Example
• Select NAME, BALANCE_CHECK(NAME)
from Worker;
IS 257 - Fall 2002
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TRIGGERS
• Create TRIGGER UPDATE_LODGING
INSTEAD OF UPDATE on
WORKER_LODGING for each row BEGIN
• if :old.name <> :new.name then update
worker set name = :new.name where
name = :old.name;
• end if;
• if :old.lodging <> … etc...
IS 257 - Fall 2002
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Next Week
• Database Administration
• More on Database Applications
IS 257 - Fall 2002
2002.10.31- SLIDE 42
