1. CS101 Introduction to Computing Lecture 20 SW Development Methodology

2. During the last lecture …
We discussed the role of programming languages in computing
We also discussed the differences among low- & high-level, interpreted & compiled, and structured & object-oriented programming languages
We also discussed the object-oriented and the structured methodologies for SW design

3. Any Other SW Design Methodologies?
Spaghetti Design Methodology
The most popular software design (programming) methodology

4. Today’s Lecture
Development process of reasonably complex SW systems does not consist of “coding” only
We will become familiar with the various phases of the process that developers follow to develop SW systems of reasonable complexity

5. SW Life-Cycle?

6. SW Life-Cycle
The sequence of phases a SW goes through from the concept to decommissioning
It is important to think about all those phases before the design work starts
Thinking about the future phases generally results in:
Shorter delivery times
Reduced costs of development
A system of higher quality

7. A Case in Point
I didn’t discuss with the customer the specs of the HW & OS before developing a particular e-commerce SW
I wrote it for the HW/OS that was easily available to me
Unfortunately that HW/OS combination differed from what was easily available to the client
Result: Huge amount of rework. Higher cost. Delayed delivery. Lower quality.
Therefore, now before designing a SW system, I first write down the installation manual, and get it OK’d by the customer. I do the same with the Operation & Maintenance manual as well.

8. Let us now take a look at a very simple SW life-cycle

9. Concept
Development
Operation & Maintenance
Decommissioning

10. That was a very simple view Now we look at a more detailed view of the life-cycle for a SW system of a reasonable size

11. Concept & Feasibility
User Requirements
Developer Specs
Planning
Design
Implementation
Integration Testing
Opr. & Maintenance
Retirement

12. During the rest of the lecture we are now going to discuss each of these steps in some detail

13. Concept: What needs to be done?
Concept & Feasibility
Concept: What needs to be done?
User Requirements
Feasibility: Preliminary exploration of possible solutions, technologies, suppliers
Developer Specs
Planning
Design
Implementation
Integration Testing
Opr. & Maintenance
Retirement

14. The user documents as much as he knows about the job the system must do
Concept & Feasibility
User Requirements
Developer Specs
Planning
Design
Implementation
Integration Testing
Opr. & Maintenance
Retirement

15. Developer analyses users requirement, performs further investigation, and produces unambiguous specifications
Concept & Feasibility
User Requirements
Developer Specs
Planning
Design
Implementation
Integration Testing
Opr. & Maintenance
Retirement

16. Detailed plan specifying the required resources and expected deliverables
Concept & Feasibility
User Requirements
Developer Specs
Planning
Design
Implementation
Integration Testing
Opr. & Maintenance
Retirement

17. Concept & Feasibility
User Requirements
Developer Specs
Architecture: Decompose the problem into subsystems and define their relationships
Planning
Design
Detailed Design: Decompose further such that one person can manage each sub-subsystem
Implementation
Integration Testing
Opr. & Maintenance
Retirement

18. Concept & Feasibility
User Requirements
Developer Specs
Planning
Design
Design
Coding
Implementation
Integration Testing
Opr. & Maintenance
Retirement

19. Concept & Feasibility
Bring the sub- subsystems together to form subsystems and test. Bring subsystems together to form the system and test
User Requirements
Developer Specs
Planning
Design
Implementation
Integration Testing
Opr. & Maintenance
Retirement

20. Use Enhance Adapt Correct Concept & Feasibility User Requirements
Developer Specs
Use
Planning
Enhance
Design
Adapt
Implementation
Integration Testing
Correct
Opr. & Maintenance
Retirement

21. Phase it out when the time comes
Concept & Feasibility
User Requirements
Developer Specs
Planning
Design
Phase it out when the time comes
Implementation
Integration Testing
Opr. & Maintenance
Retirement

22. ?

23. Concept & Feasibility
User Requirements
Test
Developer Specs
Test
Planning
Test
Design
Test
Implementation
Test
Integration Testing
Acceptance Test
Opr. & Maintenance
Retirement

24. Key Issues

25. Customer’s lack of knowledge about requirements Concept & Feasibility
User Requirements
Developer Specs
Planning
Design
Implementation
Integration Testing
Opr. & Maintenance
Retirement

26. Lag Concept & Feasibility User Requirements Developer Specs Planning
Design
Implementation
Integration Testing
Opr. & Maintenance
Retirement

27. Other Life-Cycle Models
The sequence of phases (or the life-cycle mode) that I showed is just one example of the several sequences that SW developers follow
This one is called the “Waterfall” model
You will learn about some more models (e.g. the Spiral model) in your future courses

28. Reading Assignments The Waterfall Lifecycle Model and its Derivatives

29. In Today’s Lecture
We became familiar with the various phases of the process that developers follow to develop SW systems of reasonable complexity
We looked at a couple of problems related to the Waterfall SW development model

30. Next Lecture: 2nd In the Productivity SW Series Spreadsheets
We will become familiar with the basic features and functions of spreadsheets
We will become able to perform simple data analysis using spreadsheet SW