Lawrence Chung Software Engineering: Introduction 1 Module 1: Introduction to Software Engineering

Lawrence ChungSoftware Engineering: Introduction2 Objectives What is Software Engineering? Why Software Engineering? How to do Software Engineering?

Lawrence ChungSoftware Engineering: Introduction3 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?

Lawrence ChungSoftware Engineering: Introduction4 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 1 st 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

Lawrence ChungSoftware Engineering: Introduction5 Why Software Engineering? Used w. extensive rework, but later abandoned 20% Used as delivered 2% Usable w. rework 3% 9 software projects totaling $96.7 million: Where The Money Went [Report to Congress, Comptroller General, 1979] Delivered, but never successfully used 45% Paid for, but not delivered 30% Why? Software hurts  Requirements  design

Lawrence ChungSoftware Engineering: Introduction6 What Factors Contribute to Project Success? 10. Other 9. Reliable Estimates 8. Formal Methodology 7. Firm Basic Requirements 6. Standard Software Infrastructure 5. Minimized Scope 4. Clear Business Objectives 3. Experienced Project Manager 2. User Involvement 1. Executive Management Support CHAOS The CHAOS Ten Standish Group, ‘01 ( Project Success Factors 28% 49% 23% completed on time and on budget canceled before completion overran original estimates: - Time overrun averaged 63% - Cost overrun averaged 45%

Lawrence ChungSoftware Engineering: Introduction7 What Factors Contribute to Project Failure? Standish Group, ‘01 ( CHAOS The CHAOS Ten “The definition of insanity is doing the same thing over and over again and expecting a different result.” [Albert Einstein]Albert Einstein

Lawrence ChungSoftware Engineering: Introduction8 Why Software Engineering? Work alone 20% What do software engineers do? Non-productive Activities 30% Interaction 50% programming ≠ software engineering  personal activity team activity  small, clear problem large, nebulous problem

Lawrence ChungSoftware Engineering: Introduction9 Why Software Engineering? Are you aware of any other mishaps?

Lawrence ChungSoftware Engineering: Introduction10 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]

Lawrence ChungSoftware Engineering: Introduction11 Why SE?

Lawrence ChungSoftware Engineering: Introduction12 Systems Engineering Requirements Analysis Project Planning Architectural Design Detailed Design Implementation Release Maintenance Quality Assurance Software Lifecycle Review How to Do Software Engineering? BCFH - models/languages, processes/methodologies, tools, …

Lawrence ChungSoftware Engineering: Introduction13 To be discussed later on…

Lawrence ChungSoftware Engineering: Introduction14 How to do SE?

Lawrence ChungSoftware Engineering: Introduction15 How to do SE?

Lawrence ChungSoftware Engineering: Introduction16 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! 1

Lawrence ChungSoftware Engineering: Introduction17 Genesis 11:1-9 Acts 2:1-4 The 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 understan d each other's speech. (verses five through seven).

Lawrence ChungSoftware Engineering: Introduction18 Why Did the Tower of Babel Fail? Bad communication in software projects is the root of all evil.

Lawrence ChungSoftware Engineering: Introduction19 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. 2

Lawrence ChungSoftware Engineering: Introduction20 Brook’s Law Adding manpower to a late software project makes it later.

Lawrence ChungSoftware Engineering: Introduction21 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

Lawrence ChungSoftware Engineering: Introduction22 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

Lawrence ChungSoftware Engineering: Introduction23 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? 19 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.

Lawrence ChungSoftware Engineering: Introduction24 How to do SE?

Lawrence ChungSoftware Engineering: Introduction25 How to do SE?

Lawrence ChungSoftware Engineering: Introduction26 How to do SE?

Lawrence ChungSoftware Engineering: Introduction27 How to do SE?

Lawrence ChungSoftware Engineering: Introduction28 How to do SE?

Lawrence ChungSoftware Engineering: Introduction29 How to do SE?

Lawrence ChungSoftware Engineering: Introduction30 Why speak about management rather than technical issues?

Lawrence ChungSoftware Engineering: Introduction31 How to do SE? News Groups: comp.software-eng comp.software.testing … Professional Organizations: IEEE: TSE, ICSE, ICRE, … ACM: TOSEM …

Lawrence ChungSoftware Engineering: Introduction32 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

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Lawrence ChungSoftware Engineering: Introduction40 Introduction to SE - Points to Ponder 1. Programming = software engineering? 2. What does BCFH really mean? Can you define it completely? 3. What are the similarities, and differences, between Civil Engineering and Software Engineering? 4. What are the differences between a notation and a methodology? 5. Can we use C# for analysis? 6. Can you prove you and I communicate with each other perfectly? 7. Are you a scientist or an engineer?