1. 1 Application Development in Fourth Generation Systems Semua Catatan kuliah dapat di Download dari : http://staffsite.gunadarma.ac.id/sunny

2. 2 Fourth Generation Systems Objectives: to speed up the application building process to reduce maintenance costs by making the application quick and easy to modify to make languages user friendly so that users can solve their own problems Also: to incorporate the latest advances in development techniques & technology to achieve the above

3. 3 Fourth Generation Development Users and developers collaborate Iterative Development Usually an Iterative Development the system is described graphically prototype a prototype is built based on the design evaluation and refinement of design a second and third build may be required final testing and deployment

4. 4 Fourth Generation Development... Involves: Client / Server Development Event Driven Programming Graphical User Interface (GUI) Development Object-Oriented Programming (and reuse) Database Transaction Processing

5. 5 The Application Developer must know: how to manage a database a query language (SQL & embedded SQL) system development methodologies rapid prototyping of applications Rapid Application Development Client / Server concepts GUI / Windows concepts OO programming performance tuning of the application transaction management with concurrency and locking strategies

6. 6 Developing a 4GL Application Visual Programming Environment with an interactive dialogue structure Software Engineering Support interactive testing interactive debugger code/objects reuse multiple developers configuration management

7. 7 Interactive Dialogue Structure: Screen interaction via form-filling Leads the developer (with Help and validation) Offers menu choices, lists, function keys... Default Options (developer can change default) Two dimensional (developer can click on an object, move a cursor or scroll an image...)

8. 8 Client / Server Concepts Client / Server Systems are Client / Server Systems are decomposed into three elements: servers, clients & the links between them Server: Server: provides a clearly defined set of services & a documented interface for activating those services Client: Client: requests services; processes, then displays the results Linkage: Linkage: based on telecommunications links or calls within the same processor

9. 9 Client / Server Concepts... Client / Server Connections Open Systems Open Systems the interfaces used within the system adhere to international standards Distributed Systems Distributed Systems can be categorized by what is distributed: processing, data or both OO OO objects are like servers or clients with a message interface Most common is the PC-style workstation connected over a LAN or WAN

10. 10 Client / Server Concepts... Application Development Tiers Presentation Layer - GUIs Business Rules or Application Logic Database Layer2-Tier Fat Server - data and business rules Fat Client - GUI and business rules 3-Tier or n-tier each layer on its own

11. 11 Client / Server Concepts... 4GLs and Client / Server At the Presentation Layer most 4GLs concentrate on the interface At the Business Rules Layer the business logic may be coded in the client application, be in stored database procedures and triggers or be in a separate tier At the Database Layer use wizards to generate the database 4GL Trends - 3-Tier, Distributed, OO, GUI

12. 12 GUI / Windows Concepts User Interface Design User Interface Design Ultimate goal is EASE OF USE Features Real world metaphors Selection rather than remembering Consistency User control Feedback Forgiveness Perceived stability

13. 13 GUI/Windows Concepts... A well designed screen can improve productivity by 25% Principles of Good Screen Design Principles of Good Screen Design All screens in the system should look and act consistent Cohesion: Each screen should do one complete task

14. 14 GUI / Windows Concepts... Cohesion Only data relevant to the task is on the screen Build screen L->R, Top -> Bottom Screen contents should be balanced, symmetrical Horizontal division of data better than vertical Use no more than 25% of screen Left justify data fields Use visual highlighting carefully e.g. high brightness to identify data fields Reverse video can be hard to read, but useful for errors

15. 15 GUI / Windows Concepts... The Use of Colour The Use of Colour Excessive colour can be confusing About 8% of European males are colour- blind and cannot distinguish red from green Average users remember the meaning of 5-7 colours so keep the number of colours to 4 giving the brain space for other activities

16. 16 GUI / Windows Concepts... The Use of Colour... The Use of Colour... Avoid combining colours with different perceptual depths e.g. red advances while blue recedes It is difficult to distinguish blue lines on black & yellow lines on white Use common meanings for colours e.g. red:danger, stop yellow: caution, slow green: OK, go

17. 17 GUI / Windows Concepts... Multiple Windows Multiple Windows Application design must determine the (WWS) WWS - Working Windows Set ie the number of windows the user needs in a certain time period to perform the task efficiently If the WWS cannot fit the screen the user must: search or scroll to find the required window delete windows to make room for the current one The user is distracted by “non-active” windows e.g. background tasks with activities like printing & system monitoring

18. 18 GUI / Windows Concepts... Icons Icons Are being increasingly used in GUI’s to represent functions Must be recognisable to the user Best for concrete objects, most effective as a miniature e.g. waste-paper basket = destroy Note that some symbols have different meanings in different cultures.

19. 19 Creating an Application Data Model and Data Design database (done by lecturer) Create database (done by IT Services) Create tables use SQL scripts or a software tool (Oracle Schema Manager) Populate the tables with data for testing use SQL scripts or a software tool (Oracle Enterprise Manager)

20. 20 Creating an Application... Application Design Develop the application specification Partition the application for client/server: where will the business rules be coded Identify the tasks/functions/modules Design the interaction or flow of screens ie View Navigation Diagram, Screen Hierarchy Chart or Application Flow Diagram

21. 21 Creating an Application... Application Construction Create the application include library routines and global variables Create each screen Connect to the database for data access if required Design the interface layout Set values for interface objects Write code to perform required functions: normally related to user interaction with interface objects (events) Compile and test each screen

22. 22 Creating an Application... Application Completion Test the Application Integrate all screens Exercise all use-cases Include creation of extra test cases if necessary Deploy the application create executables and DLLs, Packages etc

23. 23 Terms and Concepts Window basic visual building block of an application Event triggered by a user or by code in a script activates a block of 4GL code or script Script sequence of statements that perform processing in response to an event e.g. PL/SQL, PowerScript Control or Interface Object created by the developer to allow user to interact with the application, or to enhance the interface.

24. 24 Tutorial - to be completed by next week Create the Oracle database tables for your assignment use Oracle Schema Manager (or SQL scripts) Programs -> Oracle-> OraEMGR -> DBA Management Pack -> Schema Manager) follow carefully the table definitions given in the assignment, noting primary and foreign keys Enter data into the tables ensure data conforms to table relationships