MIS Development BBA (IT) 6 th

1. MIS DevelopmentBBA (IT) 6th (Lectures 222324) (Information System Development Methodologies) Course Lecturer: Farhan Mir

2. A methodology is ...... • a pompous word for “method” • investigation, research and discourse about methods • a set of techniques, tools, methods with some underlying philosophy

3. Information Systems Development Methodologies • Structured Analysis, Design and Implementation of Information Systems (STRADIS) • Yourdon Systems Method (YSM) • Information Engineering (IE) • Structured Systems Analysis and Design Methodology (SSADM) • Merise • Jackson Systems Development (JSD) • Object-oriented Analysis • Information Systems Work and Analysis of Changes (ISAC) • Effective Technical and Human Implementation of Computer-based Systems (ETHICS) • Soft System Methodology (SSM) • Multiview • Process Innovation • Rapid Application Development (RAD) • KADS • Euromethod

4. Some methodologies ...... with examples of specific methods • Structured methodologies • Yourdon, SSDAM, Ward-Mellor • Object-oriented methodologies • Shlaer-Mellor • Soft systems methodologies • Ethics, Multiview

5. ERDs DFDs Rich pictures STDs Structure charts Formal logics Object models Prototypes ELHs JSP Normalisation Data dictionaries PDL Decision tables / trees Some Tools

6. Each methodology will use several of these tools • with different emphasis, for different reasons, in a different order…...

7. New methodologies evolves because • perceived weaknesses in all other methodologies • changed and improved technologies • case, programming languages, hardware • changed environments, markets and needs • trends, fashion, band-wagon, legislation etc

8. A quick run through some methodologies (and methods) • What led to their rise, then to their fall; what were their tools and philosophies ?

9. Structured Methods • Probably the first methodology, after the so-called Test-and-Build i.e. “hacking”

10. Structured Methods • Structured analysis / design / programming • started in large-scale, stable, centralised corporate DP on mainframes using COBOL • “waterfall” life cycle • top-down / functional decomposition

11. Structured Methods Tools • DFDs • Structure Charts • ERDs • Data dictionaries

12. Structured Design • Technique developed to provide design guidelines • What set of programs should be • What program should accomplish • How programs should be organized into a hierarchy • Modules are shown with structure chart • Main principle of program modules • Loosely coupled – module is independent of other modules • Highly cohesive – module has one clear task

13. Structure Chart Created Using Structured Design Technique

14. Structured Analysis • Define what system needs to do (processing requirements) • Define data system needs to store and use (data requirements) • Define inputs and outputs • Define how functions work together to accomplish tasks • Data flow diagrams and entity relationship diagrams show results of structured analysis

15. Data Flow Diagram (DFD) created using Structured Analysis Technique

16. Entity-Relationship Diagram (ERD) created using the Structured Analysis technique

17. Structured Analysis Leads to Structured Design and Structured Programming

18. Problems with Structured Methods • “Paralysis-by-analysis” / “Victorian novel” • Increasingly unstable requirements : they change quicker and quicker • validation : customers / users don’t understand DFDs, ERDs etc • verification : lurch from one notation to the next

19. Problems with Structured Methods • lack of precision, completeness, consistency etc : much natural language is used in Structured Methods • lack of user involvement • feasibility sometimes poorly identified

20. More Problems with Structured Methods • Structured methods merely turn a big bit of vague text into small bits of vague text embedded in an ambiguous DFD • Even if the structured analysis is provably correct, doesn’t mean the design and source code will be ! Or the machine code !

21. Soft Systems • One response to the failings of Structured Methods

22. Origins • Structured methods deal with problems; organisations have difficulties • Most information processing systems • have substantial human / social components • are embedded in social organisations • Customers and users have partial and conflicted views on their problems

23. Soft Systems Tools • Based on systems theory • holistic not reductionist • subjective not objective • fuzzy not well-defined • purpose, boundaries, components • iterative

24. Soft Systems Tools • Root definition • precise verbal description of the essence of the processes • CATWOE • Rich pictures • to build and check a “conceptual model” that form basis of information systems

25. Soft Systems • Can be • grafted onto “front-end” of hard systems methods • have hard systems methods embedded within them • are used increasingly

26. Object-Oriented Methods • Another response to the failings of Structured Methods

27. Object-Oriented Methods • Grew out of programming • eg Smalltalk, Simula • Originally technical and academic • Intuitive : world consists of “things”, not functions • Offers framework for re-use • hence quicker quality • Now have industrial-strength methods

28. Object-Oriented Methods • Assume solution-domain will be entirely computer-based • Use one notation throughout life-cycle

29. Object-Oriented Tools • Object models • an enhanced ERD • Dynamic model • Harel charts • Process model • DFDs