Beit 381 se lec 3 - 46 - 12 feb14 - sd needs teams to develop intro

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Software Engineering, Lectures

Software Engineering, Lectures

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  • 1. SE-381 Software Engineering BEIT-V Lecture no. 3 (Basis for Software Process)
  • 2. Recap • Definitions of Sw and SE • Student’s and Industrial Strength Software • Mini Test – Retention Exercise – Comprehension Exercise • Goal – Results • Students Profiles’ Submission
  • 3. What is common between the first two clips? _____________________________________________________________ ______________ In Grocery Store Clip What two stores are compared? ______ and ________ QR Code is to __________________________________ TeSCo and E-Mart are the names for the same store (Yes/No) ----------------------- Customers of E-Mart increased by 130% after this online shopping campaign (Y/N) ____ Online Shopping Compaign Exploited Koreans 2 habits • ____________________________________ • ____________________________________ Exploited 3 widely available technologies • __________________________________________ • __________________________________________ • __________________________________________ How many customers visited the store online during the compaign? _______ Did the store became number one in off-line shopping (Y/N)? __________ At which Institute, the Four Rotor Helicopter project was carried out? __________________________ What Sw/Hw Project you can figure out from the first three clips _____________________________ _____________________________ _____________________________
  • 4. Answers to Mini Test
  • 5. From Google Earth
  • 6. North Tweaked
  • 7. What is in Today’s Lecture Covered till now – Definitions – Students’ Sw projects and Industrial Strength Sw • Software Myths – Roger S Pressman (2005) • Problem Domain – Software is Expensive, – Late and Unreliable, – Maintenance and Rework • Solution Domain – Software Engineering Challenges – Scale, – Quality & Productivity, – Consistency and Repeatability, – Change • Software Engineering Approach – Phased Development Process, – Managing the Process to get quality software
  • 8. Software Myths (‘Tonies or Ponies’) • Management Myths ( Also see ) – We already have a book that’s full of standards and procedures for building software. Won’t that provide my people with everything they need to know? – If we get behind schedule, we can add more programmers and catch up “Adding people to a late software project makes it later” – F Brooks (1975) – If I decide to outsource the software project to a 3rd party, I can just relax and let that firm build it. No substitute to misinformation
  • 9. • Customer Myths – A general statement of objectives is sufficient to begin writing programs – we can fill the details later • More information you have at start better equipped you are. – Project requirements continually change, but change can be easily accommodated because software is (not physical and) flexible • Practitioner’s Myths – Once we write the program and get it to work, our job is done • This is the start, not the end, 60% - 80% of effort will be expended after the program is deployed. For every $ spent on development needs 2 $s for its maintenance – Until I get the program running, I have no way of assessing its quality • Quality is whole some, of each part, so quality filters need to be inserted in the process for various phases of Sw Development
  • 10. – The only deliverable work product for a successful project is the working program • Documentation, data, rule base etc are all parts of software – Software Engineering will make us create voluminous and unnecessary documentation and will invariably slow us down. • Will make things easy, and lead to quicker development and easy and cost effective maintenance
  • 11. Software is Expensive • Bell 2005, quotes that US$ 500 B is spent annually for software purchase and development in USA and it is 1 % of her annual GNP (Gross National Product) • Globally US$ 1000 B is spent on Software development • Many countries exports like our neighbor’s have significant fraction coming from Sw • Pakistan currently generates 1.5 to 2 B US$ annually from Sw exports – Ref to Mr Saleem Ghori, CEO, NetSol, 2009
  • 12. Pak Software Exports • Daily Express, Islamabad, dated Feb 21, 2011 quoted Federal Bureau of Statistics that for period of July to December 2010 – Sw exports amounted to Rs 6.15 Billions, with an increase of 13.13% from its last year figure – Overseas Sw Consultancy services Rs 1.3 B – Computers Repair and support Rs 0.05 B – Computer related Auxiliary Services Rs 1.3B • Total sw exports were Rs 8.8 B with an increase of 8.37 % from previous year
  • 13. Software is Expensive
  • 14. Program Size
  • 15. Program Size C, C++40,000 KLOCWindows XP C, c++30,000 KLOCLinux C, sh100 KLOCAppache C, perl, sh320 KLOCPerl C, C++, yacc980KLOCGcc C, C++40,000 KLOCWindows XP C, c++30,000 KLOCLinux C, sh100 KLOCAppache C, perl, sh320 KLOCPerl C, C++, yacc980KLOCGcc
  • 16. Compute the Cost of a Software A software of size say 100 KLOC, like Apache web server, is to be developed by a team of professional software developers, having an average productivity of 150 LOC per person- month, and drawing an average salary of Rs 30,000/- a month.
  • 17. Program Size = 100 KLOC Average Productivity = 150 LOC / Person- Month Duration = Program Size / Productivity = 100 KLOC/150 LOC/Per-Mon = 2/3 K Per-Mon Rate = 30 K Rs / Per-Mon Total Cost = Duration * Rate = 2/3 K Per-Mon * 30 K Rs / Per-Mon = 20 K * K Rs = 20 M Rs = Rs 20,000,000
  • 18. Software – Problems and Prospects Software is Open ended, complex and key mechanism in providing the requisite functionality of the system. It is of huge size, needs 000s of people and millions of $s of investment to develop. The perceived problems in Sw development and goals the Sw Development needs to achieve are:
  • 19. • Meeting Users’ Needs • Low Cost of Production • High Performance • Portability – it works at various envisaged platforms • Low Cost of Maintenance • High Reliability • Scalability • Delivery on Time – Till to-date each of the above goals is partially achieved, so it stays as a Sw dev problem. SE seeks to provide the techniques to resolve these problems i.e. to achieve these goals.
  • 20. Software Engineering Challenges • Scale
  • 21. • Quality and Productivity
  • 22. • Consistency and Repeatability • Change
  • 23. Software Engineering Approach High Quality and Productivity (Q&P) is the basic objective of Software Engineering. The main three forces governing Q&P are:
  • 24. Software Process • Software Process is the way we produce software, it starts with the concept exploration and ends when the product is decommissioned. During this product goes through a series of phases like Requirements, Specifications, Planning, Design, Implementation, Testing, Integration, Maintenance, Documentation and finally the Retirement
  • 25. Quality Product • For a quality software product, both the quality of product itself and quality of software process is important. • The cost of error recovery in the later phases of software is many times more than the earlier phases, so higher attention should be paid in the earlier phases, and these should be made error- free.
  • 26. Software Processes – Software Process is comprised of a number of processes working in Series and in parallel to achieve the software product – These processes can be Software Development Process, Business Process, Training Process, Human Resource Management or Social Process, Quality Assurance Process, Software Monitoring and Control Process, Inspection Process and Software Management Process etc – Process is execution of a number of steps in a specified order
  • 27. Process, Project and Product – Process is a series of steps or activities conducted in an orderly manner – Project is execution of a Process, to achieve or develop a product. It is an instance of Process executed in specific time frame to get the product that meets the needs of a user – Product is the outcome of a successfully executed project – Process can be initiated on a number of Projects, and a project can yield a number of Products
  • 28. – Process works as Check List and its pre- defined stages are executed in the pre- specified order – The main objective of Software Engineering is to develop Reliable, High Quality Software that can be built within price and time budget, hence we need to focus on Software Related Processes and more precisely on Software Development Process
  • 29. Software Process • Software should be – Reliable (high quality) – Affordable (Cheap, low cost) – Small Time Cycle (so that the software could be developed speedily) • For better management and control software process should be – Phased i.e. consist of multiple stages
  • 30. Software Development Process Software Development Process Requirements Software Product In fact, this SD Process consists of: Analysis Design Implementa- tion Deployment
  • 31. And each one of these is further divided into sub phases, like Analysis Requirements Analysis Specification Design Architectural Design Lower Level or Detailed Design Implement- ation Coding Testing Unit Testing Sub-system Testing System Testing Acceptance Tst = = = = Higher Level Design
  • 32. Software Process • Software Process is the way we produce software, it starts with the concept exploration and ends when the product is decommissioned or retired. During this life, the product goes through a series of phases like Requirements, Specifications, Planning, Design, Implementation, Testing, Integration, Maintenance, Documentation and finally the Retirement
  • 33. Software Development Life Cycle • Life Cycle • All what is done on a product from its conception to its physical realization and retirement is called its Life Cycle • Software Development Life Cycle Model • It is a description of all the stages/phases that should be performed when building a software product. Number of stages differ from author to author, from 4 to 10 or even more, but in general the Classical Software Development Life Cycle model has eight (highlighted) stages
  • 34. Different Phases of SDLC Authors partition the SDLC activities differently, Eg [Jal98] mentions the following 4 stages • Requirement Analysis • Design (further divided into System Design & Detailed Des, or Jal05 mentions them as Architectural Des, High Level Des and Low Level Des) • Coding and • Testing (including Unit Testing, Integration Testing and Acceptance Testing) – Towards over-all Effort/Cost, each one of them contributed 10%, 20%, 30% and 40% respectively, and – Error distribution among the first three phases was 20%, 30% and 50% respectively
  • 35. Software Development Life Cycle (SDLC) Stage or Phases 1. Requirements Phase 2. Analysis (Specification) Phase 3. Planning Phase 4. Design Phase a. Architectural Design b. High Level Design c. Detailed Design 5. Implementation Phase 6. Integration Phase 7. Testing 8. Documentation 9. Post delivery Maintenance Phase Corrective, Perfective, Adaptive 10. Retirement Phase
  • 36. Comparative Effort Spent in Different Stages of SDLC
  • 37. Different types of Maintenance Post-delivery Maintenance • Done after deployment at the clients premises This is of two types: Corrective Maintenance or Software Repair Removal of Residual faults leaving the Specifications unchanged Enhancement or Software Update Consists of changes to specification and implementation of those changes. It further consists of two types: Perfective Maintenance The changes which client thinks will improve the effectiveness of the product, such as Additional Functionality, Decreased response time, or Optimal memory usage Adaptive Maintenance Changes made in response to changes in the environment in which the product operates, such as, a new hardware, OS or new government regulations or conformance to new standard like UNICODE
  • 38. Stage-wise Cost of SD
  • 39. Relative Costs of the Stages of SD
  • 40. Cost of Error Recovery / Correction • The cost of error recovery in the later phases of software is many times more than the earlier phases, so higher attention should be paid in the earlier phases, and respective stages/phases errors be identified and eradicated, making these phases error-free.
  • 41. Stage-wise Number of Errors
  • 42. Cost of Fixing of Errors
  • 43. Reading Assignment 1. Ch-1 Problems and Prospects, pp 3-22 From Douglas Bell (2005); Software Engineering for Students; Pearson Education Limited 2. Ch – 1 Introduction, pp 1-20 + Ch-2 From Pankaj Jalote (2005); An Integrated Approach to Software Engineering, 3rd Edition, Narosa Publishing House, New Delhi 3. Ch – 1 Introduction to Software Engineering, pp 33-50 From Roger S Pressman (2005); Software Engineering – A Practitioner’s Approach, 6th Edition, McGraw Hill Higher Education, Boston