1 R. Ching, Ph.D. MIS Dept. California State University, Sacramento Week 1 January 25 Introduction to 4GLsIntroduction to 4GLs 4GLs versus 3GLs4GLs versus

1R. Ching, Ph.D. • MIS Dept. • California State University, SacramentoR. Ching, Ph.D. • MIS Dept. • California State University, Sacramento

Week 1Week 1January 25January 25

•Introduction to 4GLsIntroduction to 4GLs•4GLs versus 3GLs4GLs versus 3GLs

•File-based systems versus databaseFile-based systems versus database


PowerBuilder 4GL ModelPowerBuilder 4GL Model

UserUser ProcessProcess DataData

Inte

rfac

eIn

terf

ace

Inte

rfac

eIn

terf

ace

ProgramProgram


Inte

rfac

e

UserUser ProcessProcess DataData

TextText ProceduralProcedural RecordsRecords

• 80 x 24 Screen80 x 24 Screen• CharactersCharacters• Function keysFunction keys

• FilesFiles• Hierarchical databaseHierarchical database

Inte

rfac

eTerm

inals

Termin

alsText

Records

Procedura

l

Procedura

l

CodeCode File-basedFile-based

• 3GL program3GL program

Conventional File-Based ApplicationsConventional File-Based Applications


Text-Based Interactive ApplicationText-Based Interactive Application

Function keys

Enter letters corresponding to a

menu options

Press function key corresponding to a

menu option


InvoiceInvoice

Account Account ReportReport

Mailing ListMailing List

File-Based SystemFile-Based System

PO ProgramPO ProgramPO ProgramPO Program

Customer Mailings Customer Mailings ProgramProgram

Customer Mailings Customer Mailings ProgramProgram

Customer AccountsCustomer AccountsProgramProgram

Customer AccountsCustomer AccountsProgramProgram

Customer Customer Order FileOrder File

One file, one program, one outputOne file, one program, one output

Customer Customer Account Account

FileFile

Customer Customer Mailing Mailing List FileList File


File-Based SystemsFile-Based Systems

• Records contain Records contain logically related logically related datadata

• Limitations:Limitations:

– Separation and isolation of dataSeparation and isolation of data

– Duplication of dataDuplication of data

• Loss of data integrityLoss of data integrity

– Data dependenceData dependence

– Incompatibility of filesIncompatibility of files

– Fixed queries/proliferation of application programsFixed queries/proliferation of application programs


Data RedundancyData Redundancy

• Customer Order FileCustomer Order File– PO numberPO number– Customer account numberCustomer account number– Customer name, address, city, state, zip codeCustomer name, address, city, state, zip code– Order dateOrder date– Product code, product description, price, unitProduct code, product description, price, unit

• Customer Account FileCustomer Account File– Account NumberAccount Number– Customer name, mailing address, city, state, zip codeCustomer name, mailing address, city, state, zip code

• Customer Mailing List FileCustomer Mailing List File– Customer name, mailing address, city, state, zip codeCustomer name, mailing address, city, state, zip code


4GL Applications4GL Applications

User Process Data

GUIGUI Event DrivenEvent Driven SetSet

• WindowsWindows• ObjectsObjects• Pictures and graphicsPictures and graphics• Point and clickPoint and click

• RDBMSRDBMS

Inte

rfac

e Work

-

Work

-

statio

ns

statio

nsGUI

Inte

rfac

e

Sets

SQLSQL

• CodeCode

DatabaseDatabase


Oracle Developer ApplicationsOracle Developer Applications

User Data

Inte

rfac

eGUI

Inte

rfac

e

Sets

Process

DataData

QueryQuery


Oracle Developer ApplicationsOracle Developer Applications

User Process Data

PresentationPresentation Data SourceData Source

File

Account #:In

terf

ace

GUI

Inte

rfac

e

Sets

• ReportsReports• FormsForms• GraphsGraphs

• Triggers Triggers (PL/SQL)(PL/SQL)

• QueryQuery


DatabaseDatabase

• ““A shared collection of logically related data (and a A shared collection of logically related data (and a description of this data), designed to meet the information description of this data), designed to meet the information needs of an organization.”needs of an organization.”


DatabaseDatabase

CustomerCustomer

OrdersOrders

Order ItemsOrder Items

ManufacturersManufacturers

ProductsProducts

DBMSDBMS

Management Management QueriesQueries

Application Application ProgramsPrograms

Other Other SoftwareSoftware

• DDLDDL• DMLDML• Controlled accessControlled access

Central RepositoryCentral Repository Single AccessSingle Access Multitude of Multitude of ApplicationsApplications


Data AbstractionData Abstraction

• Separation between the data’s structure (definition) and the Separation between the data’s structure (definition) and the application programsapplication programs

FD Master-File.FD Master-File.01 Master-Record.01 Master-Record.

05 ID05 ID PIC X(10).PIC X(10).05 Customer-Fname 05 Customer-Fname PIC X(25).PIC X(25).

..

..

..

Tightly binds the Tightly binds the data file and data file and

programprogram

In a procedural language program such as COBOL...In a procedural language program such as COBOL...




FD Master-File.FD Master-File.01 Master-Record.01 Master-Record.

05 ID05 ID PIC X(10).PIC X(10).05 Customer-Fname 05 Customer-Fname PIC X(25).PIC X(25).

..

..

..

Tightly binds the Tightly binds the data file and data file and

programprogram

DataDataOutputOutput

ProgramProgram

In a procedural language program such as COBOL...In a procedural language program such as COBOL...


DatabaseDatabase

Data and data definitionsData and data definitions

ApplicationApplication






Advantages of the Database ApproachAdvantages of the Database Approach

• Reduced redundancyReduced redundancy

• Data consistency Data consistency

• Greater informational gainGreater informational gain

– Better access to data and informationBetter access to data and information

• Improved data integrityImproved data integrity

• Improved access and securityImproved access and security

• Enforcement of standardsEnforcement of standards

• Easier modification and updatingEasier modification and updating

• Data and program independenceData and program independence

• Standardization of data accessStandardization of data access


Disadvantages of the Database ApproachDisadvantages of the Database Approach

• ComplexityComplexity

• SizeSize

• Cost of DBMSCost of DBMS

• Additional hardware costsAdditional hardware costs

• Cost of conversionCost of conversion

• PerformancePerformance

• Higher impact of failureHigher impact of failure

Stair, 1995Stair, 1995


What is a Fourth Generation Language What is a Fourth Generation Language (4GL)?(4GL)?

• ...a programming language that is less procedural and more ...a programming language that is less procedural and more English-like than third generation languages. It English-like than third generation languages. It emphasizes what is to be done more than how statements emphasizes what is to be done more than how statements are to be written.are to be written.

Stair, 1995 Stair, 1995


For example...For example...

COBOLCOBOLOPEN INPUT EMPLOYEE-FILE.OPEN INPUT EMPLOYEE-FILE.READ EMPLOYEE-FILE.READ EMPLOYEE-FILE.PERFORM WHILE NOT EOFPERFORM WHILE NOT EOF IF EMP-ID = SEARCH-KEYIF EMP-ID = SEARCH-KEY DISPLAY EMP-ID " " DISPLAY EMP-ID " " EMP-FIRST-NAME " "EMP-FIRST-NAME " " EMP-LAST-NAME " "EMP-LAST-NAME " " EMP-YTD-PAYEMP-YTD-PAY END-IFEND-IF READ EMPLOYEE-FILEREAD EMPLOYEE-FILEEND-PERFORM.END-PERFORM.

Three Control Structures:Three Control Structures:• SequenceSequence• IterationIteration• DecisionDecision


Control StructuresControl Structures


SequenceSequence




IterationIteration




DecisionDecision

FalseFalse

TrueTrue

ConditionCondition


WhatWhat as Opposed to as Opposed to HowHow


SQLSQL

SELECT EMP-ID,SELECT EMP-ID, EMP-FIRST-NAME,EMP-FIRST-NAME, EMP-LAST-NAME,EMP-LAST-NAME, EMP-YTD-PAYEMP-YTD-PAY FROM EMPLOYEEFROM EMPLOYEE WHERE EMP-ID=1234WHERE EMP-ID=1234

How to WhatHow to What


Characteristics of 4GLsCharacteristics of 4GLs

• User friendlyUser friendly– Less syntax-boundLess syntax-bound– Fewer programming skills requiredFewer programming skills required

• Non-proceduralNon-procedural– Emphasis is on Emphasis is on whatwhat (outs are desired) rather than (outs are desired) rather than howhow

(programming statements should be written)(programming statements should be written)– Shorter application development timeShorter application development time

• GUI (graphical user interface)GUI (graphical user interface)– Incorporate the use of the mouse (point and click)Incorporate the use of the mouse (point and click)– Involve the use of iconsInvolve the use of icons


Characteristics of 4GLsCharacteristics of 4GLs

• Function-basedFunction-based

– User calls upon pre-programmed functionsUser calls upon pre-programmed functions

• Specifies the arguments and parameters which Specifies the arguments and parameters which define the scope of the results define the scope of the results

– Graphical or tabular output Graphical or tabular output

• Popular for developing client/server applicationsPopular for developing client/server applications

– Toted asToted as client/server solutions client/server solutions


Other CharacteristicsOther CharacteristicsApplicable to Today’s 4GLsApplicable to Today’s 4GLs

• Menu drivenMenu driven

• Database orientedDatabase oriented

– Embedded query commands (e.g., SQL)Embedded query commands (e.g., SQL)

• Retrieval focusedRetrieval focused

– Query capabilitiesQuery capabilities

• Human factors designedHuman factors designed

Martin, 1991Martin, 1991


Menu objectMenu object

Event-driven command buttonsEvent-driven command buttons

Graphic backgroundGraphic background


SQL SQL statement statement retrieves retrieves customer customer

datadata


4GLs: Pros and Cons4GLs: Pros and Cons

• Good for ad hoc and nonrecurring reportingGood for ad hoc and nonrecurring reporting

– One-time information reportingOne-time information reporting

• Good for prototyping and end-user computing (EUC) Good for prototyping and end-user computing (EUC) application developmentapplication development

– Discovering specifications (prototyping)Discovering specifications (prototyping)

– Developing and implementing single-user applications Developing and implementing single-user applications (EUC)(EUC)

– Short learning curveShort learning curve


4GLs: Pros and Cons4GLs: Pros and Cons

• Poor computing efficiencyPoor computing efficiency

– NotNot appropriate for appropriate for

• Processing voluminous amounts of dataProcessing voluminous amounts of data

• Transaction processingTransaction processing

• Scheduled reportingScheduled reporting

• Difficult to enforce organizational computing standardsDifficult to enforce organizational computing standards

• VeryVery difficult to debug difficult to debug

• VeryVery difficult to maintain difficult to maintain


Oracle DeveloperOracle Developer

• Forms (interactive)Forms (interactive)

– Presenting information and entering data onlinePresenting information and entering data online

• Reports (reporting)Reports (reporting)

– Page-oriented display of informationPage-oriented display of information

• Graphics (charts)Graphics (charts)

– Graphic representation of dataGraphic representation of data


Documents

1 R. Ching, Ph.D. MIS Dept. California State University, Sacramento Week 1 January 25 Introduction to 4GLsIntroduction to 4GLs 4GLs versus 3GLs4GLs versus