cs 4310 software requirements engineering

CS 4310 Software Requirements Engineering

Dr. Yoonsik CheonDr. Irbis Gallegos

University of Texas at El PasoDepartment of Computer Science

Fall 2012

Introductions• CS 4310, Software Requirements Engineering

– Required course: – must pass with C or better to take 4311

• Text book: – Van Vliet, Software Engineering– Required: you will need in class sometimes.

• Course Notes: Available online• TA: TBA

Teams of 3

• Introduce yourselves• Find one food product and one movie that

you all like

• 2 minutes

Teams: Syllabus Review

• Read the syllabus• Quiz to follow• Pay attention to:

– objective: software requirements engineering– email policy– grading– attendance– office hours and policy

Quiz

• Name the other people in your group.• Two email addresses are listed on the

syllabus. What are they?• Write the pseudo code for the grading

algorithm.• What is the attendance policy?• Where is Dr. Gallegos’ new office?

Assignments

• Resume

Email

• Plan on checking your mail daily.

Fact or Fiction?

• This course is hard.• This course will take all your time.• You should concentrate on the exams and

not on the project.• You should concentrate on the project and

not the exam.• Your team mates will cover for you.

Team

What are the major steps needed to develop a reliable software system?

(5 minutes)

What is software engineering?

• Software engineering is an attempt to formalize the construction of software. In particular, we are concerned with large, complex systems, systems that require multi-person effort and usually multiple versions.

Do we need software engineering?

Do we need software engineering?

• All great software is written by small teams: look at unix (2 guys), Apple (started in a garage), …

Do we need software engineering?

• All great software is written by small teams: look at unix (2 guys), Apple (started in a garage), …

• Writing software is a creative process, an “art” or a “craft”, and cannot be engineered.

Three Critical Dimensions

Ariane 5

• June 4, 1996• European Space Agency lost newest rocket,

the Ariane 5, successor to the Ariane 4

Ariane 5• Youtube Link:http://www.youtube.com/watch?v=kYUrqdUyEpI• Youtube Summary:“The launch ended in failure due to an error in the software design caused by inadequate protection from integer overflow. This resulted in the rocket veering off its flight path 37 seconds after launch, beginning to disintegrate under high aerodynamic forces, and finally self-destructing by its automated flight termination system. The failure has become known as one of the most infamous software bugs in history. The failure resulted in a loss of more than US$370 million.”

Therac 25

• Late 1980's.• Radiation therapy device with 3 modes:

– light: for alignment– electron: low power, magnets to spread beam– X-ray: high power, flattener plate to spread

beam• Needed flattener plate in place in X-ray

operation.

Therac 25• Great Explanation and Graphics:• http://www.youtube.com/watch?

v=izGSOsAGIVQ

Others:

• 1998 GM ABS recall• 2003 East Coast Power Failure: power cut to parts

of at least 5 states (cost, $7-$10 billion)• 2004: Air traffic control system shuts down voice

communication system in southwest US, losing contact with 400 aircraft in flight.

• 2009: Washington DC Metro crash kills 9 people: train under software control at the time

Assignment Due Before Next Class• A: find two other software failures that have resulted in

significant harm (loss of life, serious risk, or loss of money) in the past 3 years. Attempt to identify the root cause of the failure.

• B: Describe two approaches to eliminating the types of software failures you identify.

• You must find no less than two independent citations for each.

• Legitimate citations include IEEE or ACM publications, web sites sponsored by Fortune 500 companies, or Prentice-Hall, Wiley, O’Rielly, Addison-Wesley, or Microsoft Press. Or anything by Parnas or McConnell.

• You must include your citations.

This is a course about:

• Recognizing, making explicit, and understanding the phases or tasks of developing software

This is a course about:

• Recognizing, making explicit, and understanding the phases or tasks of developing software

• Communicating – between stakeholders and developers– among developers– Among tasks and phases

This is a course about:

• Recognizing, making explicit, and understanding the phases or tasks of developing software

• Communicating – between stakeholders and developers– among developers– Among tasks and phases

• Building reliable, useful, correct software in cost-effective manner

Why a project?

Why a project?

• Experience is better than just spitting back what we tell you.

• Employers know this, and will ask at your interviews.

• It gives you the chance to think "outside the box" out of the context of class

"The hardest single part of building a system is deciding what to build."

Brooks. • requirements elicitation: developers and

customers discover and articulate users' needs• requirements analysis: analyze the customer and

user needs to arrive at a definition • requirements specification: develop a document • requirements verification: show the document is

correct • management of requirements: control the

process

Why software projects fail (Software Runaways, Robert Glass, 1998, Prentice)

• runaway: – fails to deliver or is 30% or more over budget

• faulty specification 51%• faulty planning and estimation 48%• based on unstable new technology 45%• inadequate management: 42%• lack of senior programming staff: 42%• problems with hardware/software from vendors: 42%

Problems with Specifications

• too many specs: project is large• unstable specs• ambiguous specs• incomplete specs

Outline of course:

• Build software teams• Interview customer, interview report• Feasibility study• Prototype• Analysis: use cases, diagrams, modeling• Specification (SRS)• Tracing