COMP 7012: Foundations of Software Engineering Spring 2012 Scott Fleming, Instructor http://flic.kr/p/3f1RGT

Great software can make the world a better place What great software has made your life better? http://flic.kr/p/4kWisE

Here’s some great software that I’ve used Facebook: Helps me connect me with old friends Photoshop: Helps me fix up my photos Subversion: Helps me manage versions of my software projects PowerPoint: Helped me produce these slides ;-)

Of course not all software is great What bad software have you encountered? http://flic.kr/p/7pGoCd

Here’s some bad software that I’ve used Facebook: Ever try to manage access control/groups? Photoshop: What does half this stuff even do? Subversion: Argh! Forgot to use svn to manage files in working copy… again Word 2009: Mind bogglingly buggy OK, so most software has pros and cons… So how can we produce software with more pros and fewer cons???

Making great software ain’t easy In fact, the “Software Crisis” has been going on since the 1960s (More like a depression) Cutter Consortium 2002 survey on litigation (78% of organizations have had disputes ending in litigation) Standish Group data on 28,000 software projects completed in 2000

In this course, you’ll learn how to reliably produce great software … … and how to avoid the bad http://flic.kr/p/9hoohu http://flic.kr/p/2v8gtd

What does software engineering mean to you? http://flic.kr/p/9ksxQa

Engineering is the creation of cost-effective solutions to practical problems by applying scientific knowledge to building things in the service of mankind Software engineering aims to do the same where “built things” are software systems http://flic.kr/p/onSfr

Let’s focus on two important challenges in SE (1) Giving the customers what they want http://flic.kr/p/6X2iPV (2) Cost-effectiveness http://flic.kr/p/2UJezY

Problem: Requirements http://flic.kr/p/a5UCs

“The customer is always right!” But … Customers may change their minds Customers may not agree with each other Customers may not know exactly what they want http://flic.kr/p/9XVhuK

Problem: Cost estimation http://flic.kr/p/anRib

Spectacular failure: Denver Int’l Airport baggage-handling system Largest international airport in the US Scheduled to open in Oct ‘93; actually opened in Feb ‘95 Had to buy back up system and scale back first system after deadline had passed System never did work as intended and was retired in 2005 Problems both managerial and technical Hard to get precise figures on how over-budget, but one estimate at $3.2 billion

Problem: Bugs http://flic.kr/p/6Pxibn

Spectacular failure: Therac-25 radiation therapy machine 6 overdoses between Jun ‘85 and Jan ‘87. First overdose: Breast cancer “tremendous force of heat… this red-hot sensation” Reddening, swelling in front; later matching back; tremendous pain Lost breast and lost use of arm, shoulder 15,000-20,000 rad overdose; 200 rad normal dose; 1000 to whole body will kill Manufacturer and operators refused to implicate Therac-25 Other cases were similar; one for skin cancer on face resulted in death in one month

Problem: Maintenance http://flic.kr/p/5U934t

All successful software will change over time But such change can lead to design erosion

What ways have you heard of for coping with these problems? http://flic.kr/p/9ksxQa

Iterative development Test-driven development In this course, you’ll use four approaches for coping with the challenges of software engineering Agile development Iterative development Test-driven development Object-oriented analysis and design http://flic.kr/p/a314v9

Values of Agile Development From the Agile Manifesto Individuals and interactions over processes and tools Working software over comprehensive documentation Customer collaboration over contract negotiation Responding to change over following a plan http://flic.kr/p/6Ag67y

Iterative development process Go around and around in this loop Each time around is an iteration Iterations are timeboxed

Test-driven development Write the tests before the code!

Object-oriented analysis and design OOA applies object modeling to understand the requirements for the system (i.e., what the system should do) OOD elaborates analysis models specify how the system should work (i.e., how the system should do it) http://flic.kr/p/NT667

OOA/D is best understood with an example Consider a dice game in which software simulates a player rolling two dice. If the total is seven, the player wins Otherwise, he/she loses Example from Larman (2005) http://flic.kr/p/4AuKRy

Define use cases UC Play a dice game: Analysis Use cases Player requests to roll the dice. System presents results. If the dice face value totals seven, player wins; otherwise player loses Design

Define a domain model Analysis Use cases Domain model Design

Assign object responsibilities and draw interaction diagrams Analysis Use cases Domain model Design Interaction diagrams

Define design class diagrams Analysis Use cases Domain model Design Interaction diagrams Design class diagrams

Why is this OOA/D process useful? http://flic.kr/p/9ksxQa

Why is this OOA/D process useful? Lowers representation gap between software components and our mental models of the problem domain

How does OOA/D fit into an iterative process? http://flic.kr/p/9ksxQa

Closing thought: To effectively apply these approaches requires a lot of experience Let’s take a look at the syllabus to see how you’re going to get that experience