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Module 1: Introduction to Software Engineering

Module 1: Introduction to Software Engineering

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Module 1: Introduction to Software Engineering

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  1. Module 1: Introduction to Software Engineering Software Engineering: Introduction

  2. Objectives • What is Software Engineering? • Why Software Engineering? • How to do Software Engineering? Software Engineering: Introduction

  3. What is Software Engineering? Software Engineering = Software + Engineering • What is Software? Software = Soft + ware Any examples? • What is Engineering? Engineering = Engine-er-ing Any examples? Is this an Engineering discipline? If yes, why? If not, why not? Is this for an Engineer or a scientist? Software Engineering: Introduction

  4. What is Software Engineering? A historical definition: “The establishment and use of sound engineering principles in order to obtain economically software that is reliable and works efficiently on real machines …” [Fritz Bauer, at the 1st NATO Conference on Software Engineering, 1969] IEEE definition: “Software engineering is the application of a systematic, disciplined, quantifiable approach to the development, operation, and maintenance of software; that is, the application of engineering to software.” A shorter definition: BCFH Software Engineering: Introduction

  5. Why Software Engineering? 9 software projects totaling $96.7 million: Where The Money Went [Report to Congress, Comptroller General, 1979] Delivered, but never successfully used 45% Used as delivered 2% Paid for, but not delivered 30% Usable w. rework 3% • Why? • Software hurts • Requirements • design Used w. extensive rework, but later abandoned 20% Software Engineering: Introduction

  6. The CHAOS Ten 1. Executive Management Support 2. User Involvement 3. Experienced Project Manager 4. Clear Business Objectives 5. Minimized Scope 6. Standard Software Infrastructure 7. Firm Basic Requirements 8. Formal Methodology 9. Reliable Estimates 10. Other What Factors Contribute to Project Success? Standish Group, ‘01 (www.standishgroup.com) Project Success Factors 28% completed on time and on budget • overran original estimates: • Time overrun averaged 63% • - Cost overrun averaged 45% canceled before completion 49% 23% Software Engineering: Introduction

  7. What Factors Contribute to Project Failure? The CHAOS Ten The CHAOS Ten Standish Group, ‘01 (www.standishgroup.com) Software Engineering: Introduction “The definition of insanity is doing the same thing over and over again and expecting a different result.” [Albert Einstein]

  8. Why Software Engineering? What do software engineers do? Non-productive Activities 30% Interaction 50% Work alone 20% • programming ≠ software engineering • personal activity team activity • small, clear problem large, nebulous problem Software Engineering: Introduction

  9. Why Software Engineering? http://www.cis.gsu.edu/~mmoore/CIS3300/handouts/SciAmSept1994.html http://techdirt.com/articles/20060818/1613226.shtml Are you aware of any other mishaps? Software Engineering: Introduction

  10. Why Software Engineering? Major symptoms of the “software crises”: • Over budget • Schedule slippage • Poor quality Major causes of the “software crises”: The "software crises" came about when people realized the major problems in software development were … caused by communication difficulties and the management of complexity” [Budd] Software Engineering: Introduction

  11. Why SE? Software Engineering: Introduction

  12. How to Do Software Engineering? Software Lifecycle Review Systems Engineering Requirements Analysis Quality Assurance Project Planning Maintenance Architectural Design Detailed Design Implementation BCFH - models/languages, processes/methodologies, tools, … Release Software Engineering: Introduction

  13. To be discussed later on… Software Engineering: Introduction

  14. How to do SE? Software Engineering: Introduction

  15. How to do SE? Software Engineering: Introduction

  16. The Tar Pit • The woes of the craft: • Bugs!!! • Bugs get harder as testing progresses • The fundamental problem: fixing a bug has a 20%-50% chance of introducing another • The product gets obsolete upon or even before completion • Worse: must use others’ programs! Software Engineering: Introduction

  17. Genesis 11:1-9 Acts 2:1-4The Tower Of Babel Let's become famous by building a city with a tower that reaches up to heaven (verse four). Let's go down and confuse their speech right away, and make it so that they will not understand each other's speech. (verses five through seven). Software Engineering: Introduction

  18. Why Did the Tower of Babel Fail? Bad communication in software projects is the root of all evil. Software Engineering: Introduction

  19. The Mythical Man-Month • Optimism: • All programmers are optimists, believing in happy endings and fairy god-mothers. • Because programming tasks are usually chained end-to-end, the probability that each will go well is very small. • Man-month: • Cost vary as a product: men· months. • Progress does not: communication overhead! • Overhead: intercommunication and training. Software Engineering: Introduction

  20. Brook’s Law Adding manpower to a late software project makes it later. Software Engineering: Introduction

  21. Hatching a Catastrophe Poor Project planning, estimation, control • Coding is “90% finished” for half of the total coding time • Debugging is “99% complete” most of the time Software Engineering: Introduction

  22. No Silver Bullet – Essence and Accident in Software Engineering “There is no single development, in either technology or management technique, which by itself promises even one order-of-magnitude improvement within a decade in productivity, in reliability, in simplicity” (1986). • Complexity • enormous number of states (orders of magnitude more than in hardware), so conceiving, describing and testing is hard • increases non-linearly with its size • introduces a lot of difficulties: • communication among team members • enumerating (much less understanding) of all possible states of the program • management problems: • conceptual integrity is hard to achieve • learning curve: personnel turnover becomes disaster • others Software Engineering: Introduction

  23. The M-MM after 20 years Answers questions like: What do you now think was wrong when written? What is now obsolete? What is really new in the software engineering world? • What was right and still is: • Conceptual integrity is the more important factor in ease of use [There are other factors. Consider Macintosh vs. MS-DOS].It is the central question addresses by M-MM and is central to product quality. Software Engineering: Introduction

  24. How to do SE? Software Engineering: Introduction

  25. How to do SE? Software Engineering: Introduction

  26. How to do SE? Software Engineering: Introduction

  27. How to do SE? Software Engineering: Introduction

  28. How to do SE? Software Engineering: Introduction

  29. How to do SE? Software Engineering: Introduction

  30. Why speak about management rather than technical issues? Software Engineering: Introduction

  31. How to do SE? • News Groups: comp.software-eng comp.software.testing … • Professional Organizations: IEEE: TSE, ICSE, ICRE, … ACM: TOSEM … Software Engineering: Introduction

  32. Introduction to SE - Summary Why • Software Crisis due to Communication and Complexity • Inherent complexity What • Engineering (large) software, bcfh How • BCFH languages, concepts, models, tools Software Engineering: Introduction

  33. Software Engineering: Introduction

  34. Software Engineering: Introduction

  35. Software Engineering: Introduction

  36. Software Engineering: Introduction

  37. Software Engineering: Introduction

  38. Software Engineering: Introduction

  39. Software Engineering: Introduction

  40. Introduction to SE - Points to Ponder • Programming = software engineering? • What does BCFH really mean? Can you define it completely? • What are the similarities, and differences, between Civil Engineering and Software Engineering? • What are the differences between a notation and a methodology? • Can we use C# for analysis? • Can you prove you and I communicate with each other perfectly? • Are you a scientist or an engineer? Software Engineering: Introduction