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

2. 2 R. Ching, Ph.D. MIS Dept. California State University, Sacramento PowerBuilder 4GL Model UserProcessData InterfaceInterface Program

3. 3 R. Ching, Ph.D. MIS Dept. California State University, Sacramento Interface UserProcessData TextProceduralRecords 80 x 24 Screen80 x 24 Screen CharactersCharacters Function keysFunction keys FilesFiles Hierarchical databaseHierarchical database Interface Terminals Text Records ProceduralCode File-based 3GL program3GL program Conventional File-Based Applications

4. 4 R. Ching, Ph.D. MIS Dept. California State University, Sacramento Text-Based Interactive Application Function keys Enter letters corresponding to a menu options Press function key corresponding to a menu option

5. 5 R. Ching, Ph.D. MIS Dept. California State University, Sacramento Invoice Account Report Mailing List File-Based System PO Program Customer Mailings Program Program Customer Accounts Program Program Customer Order File One file, one program, one output Customer Account File Customer Mailing List File

6. 6 R. Ching, Ph.D. MIS Dept. California State University, Sacramento File-Based Systems Records contain logically related dataRecords contain logically related data Limitations:Limitations: –Separation and isolation of data –Duplication of data Loss of data integrityLoss of data integrity –Data dependence –Incompatibility of files –Fixed queries/proliferation of application programs

7. 7 R. Ching, Ph.D. MIS Dept. California State University, Sacramento Data Redundancy Customer Order FileCustomer Order File –PO number –Customer account number –Customer name, address, city, state, zip code –Order date –Product code, product description, price, unit Customer Account FileCustomer Account File –Account Number –Customer name, mailing address, city, state, zip code Customer Mailing List FileCustomer Mailing List File –Customer name, mailing address, city, state, zip code

8. 8 R. Ching, Ph.D. MIS Dept. California State University, Sacramento 4GL Applications UserProcessData GUI Event Driven Set WindowsWindows ObjectsObjects Pictures and graphicsPictures and graphics Point and clickPoint and click RDBMSRDBMS Interface Work-stations GUI Interface Sets SQL CodeCode Database

9. 9 R. Ching, Ph.D. MIS Dept. California State University, Sacramento Oracle Developer Applications UserData Interface GUI Interface Sets Process Data Query

10. 10 R. Ching, Ph.D. MIS Dept. California State University, Sacramento Oracle Developer Applications UserProcessData Presentation Data Source File Account #: Interface GUI Interface Sets ReportsReports FormsForms GraphsGraphs Triggers (PL/SQL)Triggers (PL/SQL) QueryQuery

11. 11 R. Ching, Ph.D. MIS Dept. California State University, Sacramento Database “A shared collection of logically related data (and a description of this data), designed to meet the information needs of an organization.”“A shared collection of logically related data (and a description of this data), designed to meet the information needs of an organization.”

12. 12 R. Ching, Ph.D. MIS Dept. California State University, Sacramento Database Customer Orders Order Items Manufacturers Products DBMS Management Queries Application Programs Other Software DDLDDL DMLDML Controlled accessControlled access Central Repository Single Access Multitude of Applications

13. 13 R. Ching, Ph.D. MIS Dept. California State University, Sacramento Data Abstraction Separation between the data’s structure (definition) and the application programsSeparation between the data’s structure (definition) and the application programs FD Master-File. 01 Master-Record. 05 IDPIC X(10). 05 Customer-Fname PIC X(25).... Tightly binds the data file and program In a procedural language program such as COBOL...

14. 14 R. Ching, Ph.D. MIS Dept. California State University, Sacramento Data Abstraction Separation between the data’s structure (definition) and the application programsSeparation between the data’s structure (definition) and the application programs FD Master-File. 01 Master-Record. 05 IDPIC X(10). 05 Customer-Fname PIC X(25).... Tightly binds the data file and program Data Output Program In a procedural language program such as COBOL...

15. 15 R. Ching, Ph.D. MIS Dept. California State University, Sacramento Database Data and data definitions Application Application Application Data Abstraction Separation between the data’s structure (definition) and the application programsSeparation between the data’s structure (definition) and the application programs

16. 16 R. Ching, Ph.D. MIS Dept. California State University, Sacramento Advantages of the Database Approach Reduced redundancyReduced redundancy Data consistencyData consistency Greater informational gainGreater informational gain –Better 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

17. 17 R. Ching, Ph.D. MIS Dept. California State University, Sacramento Disadvantages 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 failure Stair, 1995Higher impact of failure Stair, 1995

18. 18 R. Ching, Ph.D. MIS Dept. California State University, Sacramento What is a Fourth Generation Language (4GL)?...a programming language that is less procedural and more English-like than third generation languages. It emphasizes what is to be done more than how statements are to be written. Stair, 1995...a programming language that is less procedural and more English-like than third generation languages. It emphasizes what is to be done more than how statements are to be written. Stair, 1995

19. 19 R. Ching, Ph.D. MIS Dept. California State University, Sacramento For example... COBOL OPEN INPUT EMPLOYEE-FILE. READ EMPLOYEE-FILE. PERFORM WHILE NOT EOF IF EMP-ID = SEARCH-KEY IF EMP-ID = SEARCH-KEY DISPLAY EMP-ID " " DISPLAY EMP-ID " " EMP-FIRST-NAME " " EMP-FIRST-NAME " " EMP-LAST-NAME " " EMP-LAST-NAME " " EMP-YTD-PAY EMP-YTD-PAY END-IF END-IF READ EMPLOYEE-FILE READ EMPLOYEE-FILEEND-PERFORM. Three Control Structures: SequenceSequence IterationIteration DecisionDecision

20. 20 R. Ching, Ph.D. MIS Dept. California State University, Sacramento Control Structures COBOL OPEN INPUT EMPLOYEE-FILE. READ EMPLOYEE-FILE. PERFORM WHILE NOT EOF IF EMP-ID = SEARCH-KEY IF EMP-ID = SEARCH-KEY DISPLAY EMP-ID " " DISPLAY EMP-ID " " EMP-FIRST-NAME " " EMP-FIRST-NAME " " EMP-LAST-NAME " " EMP-LAST-NAME " " EMP-YTD-PAY EMP-YTD-PAY END-IF END-IF READ EMPLOYEE-FILE READ EMPLOYEE-FILEEND-PERFORM. Sequence

21. 21 R. Ching, Ph.D. MIS Dept. California State University, Sacramento Control Structures COBOL OPEN INPUT EMPLOYEE-FILE. READ EMPLOYEE-FILE. PERFORM WHILE NOT EOF IF EMP-ID = SEARCH-KEY IF EMP-ID = SEARCH-KEY DISPLAY EMP-ID " " DISPLAY EMP-ID " " EMP-FIRST-NAME " " EMP-FIRST-NAME " " EMP-LAST-NAME " " EMP-LAST-NAME " " EMP-YTD-PAY EMP-YTD-PAY END-IF END-IF READ EMPLOYEE-FILE READ EMPLOYEE-FILEEND-PERFORM. Iteration

22. 22 R. Ching, Ph.D. MIS Dept. California State University, Sacramento Control Structures COBOL OPEN INPUT EMPLOYEE-FILE. READ EMPLOYEE-FILE. PERFORM WHILE NOT EOF IF EMP-ID = SEARCH-KEY IF EMP-ID = SEARCH-KEY DISPLAY EMP-ID " " DISPLAY EMP-ID " " EMP-FIRST-NAME " " EMP-FIRST-NAME " " EMP-LAST-NAME " " EMP-LAST-NAME " " EMP-YTD-PAY EMP-YTD-PAY END-IF END-IF READ EMPLOYEE-FILE READ EMPLOYEE-FILEEND-PERFORM. Decision False True Condition

23. 23 R. Ching, Ph.D. MIS Dept. California State University, Sacramento What as Opposed to How COBOL OPEN INPUT EMPLOYEE-FILE. READ EMPLOYEE-FILE. PERFORM WHILE NOT EOF IF EMP-ID = SEARCH-KEY IF EMP-ID = SEARCH-KEY DISPLAY EMP-ID " " DISPLAY EMP-ID " " EMP-FIRST-NAME " " EMP-FIRST-NAME " " EMP-LAST-NAME " " EMP-LAST-NAME " " EMP-YTD-PAY EMP-YTD-PAY END-IF END-IF READ EMPLOYEE-FILE READ EMPLOYEE-FILEEND-PERFORM.SQL SELECT EMP-ID, EMP-FIRST-NAME, EMP-FIRST-NAME, EMP-LAST-NAME, EMP-LAST-NAME, EMP-YTD-PAY EMP-YTD-PAY FROM EMPLOYEE FROM EMPLOYEE WHERE EMP-ID=1234 WHERE EMP-ID=1234 How to What

24. 24 R. Ching, Ph.D. MIS Dept. California State University, Sacramento Characteristics of 4GLs User friendlyUser friendly –Less syntax-bound –Fewer programming skills required Non-proceduralNon-procedural –Emphasis is on what (outs are desired) rather than how (programming statements should be written) –Shorter application development time GUI (graphical user interface)GUI (graphical user interface) –Incorporate the use of the mouse (point and click) –Involve the use of icons

25. 25 R. Ching, Ph.D. MIS Dept. California State University, Sacramento Characteristics of 4GLs Function-basedFunction-based –User calls upon pre-programmed functions Specifies the arguments and parameters which define the scope of the resultsSpecifies the arguments and parameters which define the scope of the results –Graphical or tabular output Popular for developing client/server applicationsPopular for developing client/server applications –Toted as client/server solutions

26. 26 R. Ching, Ph.D. MIS Dept. California State University, Sacramento Other Characteristics Applicable to Today’s 4GLs Menu drivenMenu driven Database orientedDatabase oriented –Embedded query commands (e.g., SQL) Retrieval focusedRetrieval focused –Query capabilities Human factors designed Martin, 1991Human factors designed Martin, 1991

27. 27 R. Ching, Ph.D. MIS Dept. California State University, Sacramento Menu object Event-driven command buttons Graphic background

28. 28 R. Ching, Ph.D. MIS Dept. California State University, Sacramento SQL statement retrieves customer data

29. 29 R. Ching, Ph.D. MIS Dept. California State University, Sacramento 4GLs: Pros and Cons Good for ad hoc and nonrecurring reportingGood for ad hoc and nonrecurring reporting –One-time information reporting Good for prototyping and end-user computing (EUC) application developmentGood for prototyping and end-user computing (EUC) application development –Discovering specifications (prototyping) –Developing and implementing single-user applications (EUC) –Short learning curve

30. 30 R. Ching, Ph.D. MIS Dept. California State University, Sacramento 4GLs: Pros and Cons Poor computing efficiencyPoor computing efficiency –Not 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 Very difficult to debugVery difficult to debug Very difficult to maintainVery difficult to maintain

31. 31 R. Ching, Ph.D. MIS Dept. California State University, Sacramento Oracle Developer Forms (interactive)Forms (interactive) –Presenting information and entering data online Reports (reporting)Reports (reporting) –Page-oriented display of information Graphics (charts)Graphics (charts) –Graphic representation of data

32. 32 R. Ching, Ph.D. MIS Dept. California State University, Sacramento