Fourth Generation Languages and PHP

IS 257 - Fall 2002 2002.10.31- SLIDE 1

Fourth Generation Languages and PHP

University of California, Berkeley

School of Information Management and Systems

SIMS 257: Database Management

IS 257 - Fall 2002 2002.10.31- SLIDE 2

Lecture Outline

• Review: Security and Integrity

• Fourth Generation Languages

• More on PHP and Web Interfaces

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Lecture Outline




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Security and Integrity Functions in Database Administration

• Data Integrity

• Security Management

• Backup and Recovery

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Security and Integrity Functions in Database Administration

• Data Integrity

• Security Management

• Backup and Recovery

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Integrity Constraints (review)

• The constraints we wish to impose in order to protect the database from becoming inconsistent.

• Five types– Required data– attribute domain constraints– entity integrity– referential integrity– enterprise constraints

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Data and Domain Integrity

• This is now increasing handled by the database. In Oracle, for example, when defining a table you can specify:

• CREATE TABLE table-name (

attr2 attr-type NOT NULL, forbids NULL values

attrN attr-type CHECK (attrN = UPPER(attrN) verifies that the data meets certain criteria

attrO attr-type DEFAULT default_value); Supplies default values

IS 257 - Fall 2002 2002.10.31- SLIDE 8

Referential Integrity

• Ensures that dependent relationships in the data are maintained. In Oracle, for example:

• CREATE TABLE table-name ( attr1 attr-type PRIMARY KEY, attr2 attr-type NOT NULL,…, attrM attr-type REFERENCES

owner.tablename(attrname) ON DELETE CASCADE, …

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Concurrency Control

• The goal is to support access by multiple users to the same data, at the same time

• It must assure that the transactions are serializable and that they are isolated

• It is intended to handle several problems in an uncontrolled system

• Specifically:– Lost updates– Inconsistent data states during access– Uncompleted (or committed) changes to data

IS 257 - Fall 2002 2002.10.31- SLIDE 10

Transaction Control in ORACLE

• Transactions are sequences of SQL statements that ORACLE treats as a unit– From the user’s point of view a private copy of the

database is created for the duration of the transaction

• Transactions are started with SET TRANSACTION, followed by the SQL statements

• Any changes made by the SQL are made permanent by COMMIT

• Part or all of a transaction can be undone using ROLLBACK

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Transactions in ORACLE

• COMMIT;• SET TRANSACTION READ ONLY;• SELECT NAME, ADDRESS FROM WORKERS;• SELECT MANAGER, ADDRESS FROM

PLACES;• COMMIT;• Freezes the data for the user in both tables before either

select retrieves any rows, so that changes that occur concurrently will not show up

• Commits before and after ensure any uncompleted transactions are finish, and then release the frozen data when done

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Transactions in ORACLE

• Savepoints are places in a transaction that you may ROLLBACK to (called checkpoints in other DBMS)– SET TRANACTION…;– SAVEPOINT ALPHA;– SQL STATEMENTS…– IF (CONDITION) THEN ROLLBACK TO SAVEPOINT

ALPHA;– SAVEPOINT BETA;– SQL STATEMENTS…– IF …;– COMMIT;

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Database Security

• Views or restricted subschemas• Authorization rules to identify users and

the actions they can perform• User-defined procedures (and rule

systems) to define additional constraints or limitations in using the database

• Encryption to encode sensitive data• Authentication schemes to positively

identify a person attempting to gain access to the database

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Views

• A subset of the database presented to some set of users– SQL:

CREATE VIEW viewname AS SELECT field1, field2, field3,…, FROM table1, table2 WHERE <where clause>;

– Note: “queries” in Access function as views

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Restricted Views

• Main relation has the form:

Name C_name Dept C_dept Prof C_prof TC

J Smith S Dept1 S Cryptography TS TS

M Doe U Dept2 S IT Security S S

R Jones U Dept3 U Secretary U U

U = unclassified : S = Secret : TS = Top Secret

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Restricted Views

NAME Dept Prof

J Smith Dept1 ---

M Doe Dept2 IT Security

R Jones Dept3 Secretary

NAME Dept Prof

M Doe --- ---

R Jones Dept3 Secretary

S-view of the data

U-view of the data

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Disaster Recovery Planning

Testing andTraining

ProceduresDevelopment

Budget &Implement

PlanMaintenance

RecoveryStrategies

RiskAnalysis

From Toigo “Disaster Recovery Planning”

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Threats to Assets and Functions

• Water

• Fire

• Power Failure

• Mechanical breakdown or software failure

• Accidental or deliberate destruction of hardware or software– By hackers, disgruntled employees, industrial

saboteurs, terrorists, or others

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Threats

• Between 1967 and 1978 fire and water damage accounted for 62% of all data processing disasters in the U.S.

• The water damage was sometimes caused by fighting fires

• More recently improvements in fire suppression (e.g., Halon) for DP centers has meant that water is the primary danger to DP centers

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Lecture Outline




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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??

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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

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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.

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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

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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

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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

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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

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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.

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• 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.

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• 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

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• 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?

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Components of a 4GL

Application Parameters

Testingtools/debugger

InterpreterOptimizingcompiler

RulesSpecification

DataSpecification

ReportSpecification

ScreenSpecification

Proceduralfacility

Feedback

for building routine applications…

IS 257 - Fall 2002 2002.10.31- SLIDE 33

5GLs -- Natural Language

• Possibilities

• Problems

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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

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Natural Language

• 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

• It should be combined with other dialogue contructs that aid in the representation of precise logic and structures

James Martin, Fourth Generation Languages, 1985

Disadvantages of using NL Appropriate response to the disadvantage

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Natural Language

• It takes substantial time to key in sentences

• Ambiguities are possible

• Substantial processing is needed

• 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

Disadvantages of using NL Appropriate response to the disadvantage

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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?

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Lecture Outline




IS 257 – Spring 2004 2004.02.26 - SLIDE 39

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 – Spring 2004 2004.02.26 - SLIDE 40

PHP Syntax

• Similar to ASP

• Includes most programming structures (Loops, functions, Arrays, etc.)

• Loads HTML form variables so that they are addressable by name

<HTML><BODY>

<?php

$myvar = “Hello World”;

echo $myvar ;

?>

</BODY></HTML>

IS 257 – Spring 2004 2004.02.26 - SLIDE 41

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>

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Diveshop PHP

• The same interface (with minor differences) that we saw for ColdFusion has been implemented in PHP and MySQL

• Address for the example is – http://dream.sims.berkeley.edu/~ray/Diveshop/index.php3

• To setup your own MySQL database you will need to use the “my.sims” interface to request a MySQL account and PHP access

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Diveshop PHP

• Setup puts a “public_html.php” directory in your home directory and you put your PHP files there

• The PHP processor is on the “dream.sims” machine, so use that for access

• Because the results of the PHP processing don’t include the original PHP instructions we will look at the different PHP scripts that generated the pages

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Simple search <html><head><title>Example PHP Database: DiveShop</title></head><body><CENTER><font size=+2 face="arial,helvetica">PHP DiveShop Customers</font><p><IMG SRC="LOGO.GIF" ></CENTER><p>

<table border=0 cellpadding=2 cellspacing=2 width=110%><tr><td>ID #</td><td><b> <font face="arial,helvetica">Name</td><td>Street</td><td>City</td><td>State/Prov</td><td>Zip</td><td>Country</td><td>Phone</td><td>First Contact</td></tr><tr><td colspan=9><hr width=100% noshade></td></tr>

<? mysql_connect("localhost","ray","ray"); $query = "SELECT * FROM DIVECUST"; $result = mysql_db_query("ray", $query); if ($result) { echo "Got results..."; while ($r = mysql_fetch_array($result)) { echo "<tr>";

$tmp = $r["Customer_No"]; echo "<td>$tmp</td>";

$tmp = $r["Name"]; echo "<td>$tmp</td>";

$tmp = $r["Street"]; echo "<td>$tmp</td>";

$tmp = $r["City"]; echo "<td>$tmp</td>";

$tmp = $r["State_Prov"]; echo "<td>$tmp</td>";

$tmp = $r["Zip_Postal_Code"]; echo "<td>$tmp</td>";

$tmp = $r["Country"]; echo "<td>$tmp</td>";

$tmp = $r["Phone"]; echo "<td>$tmp</td>";

$tmp = $r["First_Contact"]; echo "<td>$tmp</td>";

echo "</tr>"; } } else { echo "<p>No Results???"; }?></table></body></html>

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Details<? mysql_connect("localhost","ray","ray"); $query = "SELECT * FROM DIVECUST"; $result = mysql_db_query("ray", $query); if ($result) { echo "Got results..."; while ($r = mysql_fetch_array($result)) { echo "<tr>";

$tmp = $r["Customer_No"]; echo "<td>$tmp</td>";

$tmp = $r["Name"];…etc…} } else { echo "<p>No Results???"; }?>

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Adding data<!doctype html public "-//w3c//dtd html 4.0 transitional//en"><html><head> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> <meta name="GENERATOR" content="Mozilla/4.75 [en]C-CCK-MCD (WinNT; U) [Netscape]"> <title>New Customer Information</title></head><body bgcolor="#FFFFFF">

<h2><img SRC="LOGO.GIF" align=LEFT><b><font color="#0000FF"><font size=+4>DiveShop</font></font></b>:New Customer Input</h2>

<hr><form ACTION="procform.php3" METHOD=GET><h2>Please input your information below</h2>Name: <input NAME=name TYPE=TEXT SIZE=100><br>Street: <input NAME=street TYPE=TEXT SIZE=100><br>City: <input NAME=city TYPE=TEXT SIZE=100><br>State: <input NAME=state TYPE=TEXT SIZE=2><br>ZIP: <input NAME=Zip TYPE=TEXT SIZE=12><br>Country: <input NAME=Country TYPE=TEXT SIZE=50><br>Phone: <input NAME=Phone TYPE=TEXT SIZE=50><p><input TYPE=submit VALUE=" Submit Data "><input type=reset VALUE=" Clear Fields "></form><hr></body></html>

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Fourth Generation Languages and PHP