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Software EngineeringSoftware Engineering

CS 421 / SWE 421 CS 421 / SWE 421 Kinga DobolyiKinga Dobolyi

Why are you taking this course?

Alternatively, why are we teaching this course? Do you need a course in software engineering? How is writing the code for a 211 project

different from software engineering (or is it)? What do you think we will be focusing on in this

class?

What is Software Engineering?What is Software Engineering?

According to Wikipedia: According to Wikipedia: ““Software Software engineeringengineering ( (SESE) is a profession dedicated ) is a profession dedicated

to designing, to designing,

implementing, and implementing, and

modifying software so modifying software so

that it is of that it is of higher qualityhigher quality,,

more more affordableaffordable, ,

maintainablemaintainable, and , and faster faster

to buildto build””

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Why worry about SW Why worry about SW Engineering?Engineering?

Quality issues: History of SW failures from Quality issues: History of SW failures from http://www.wired.com/software/coolapps/news/2005/11/69355

Many more incidents…Many more incidents…

Software is expensive to Software is expensive to maintainmaintain

Maintenance activities consume 70-90% of the Maintenance activities consume 70-90% of the total lifecycle cost of software, summing to over total lifecycle cost of software, summing to over $70 billion per year$70 billion per year

We want to “get it right” the first timeWe want to “get it right” the first time But as we’ll see this is non-trivialBut as we’ll see this is non-trivial

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Why is it so hard?Why is it so hard?

Lots of “parts”. Many more thanLots of “parts”. Many more than

mechanical devicesmechanical devices Dishwasher - 128 partsDishwasher - 128 parts Car - 14,000 partsCar - 14,000 parts Space shuttle - 2.5 million partsSpace shuttle - 2.5 million parts Red Hat Linux 7.1 - 30 million source lines of code (SLOC)Red Hat Linux 7.1 - 30 million source lines of code (SLOC) Mac Office - 30 million SLOCMac Office - 30 million SLOC

Using 70 programmers = 428,000 SLOC / programmerUsing 70 programmers = 428,000 SLOC / programmer But those are big… what about “normal size programs”?But those are big… what about “normal size programs”?

Average programmer SLOC (Source lines of code) / day = 100Average programmer SLOC (Source lines of code) / day = 100 5 days/week * 52 weeks/year = 26,000 SLOC / year5 days/week * 52 weeks/year = 26,000 SLOC / year 15 programmer team = 390,000 SLOC / year15 programmer team = 390,000 SLOC / year

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Why is it so hard? (continued)Why is it so hard? (continued)

We’re a young field We’re a young field ENIAC/ MARK-I in 1946ENIAC/ MARK-I in 1946 FORTRAN - 1957FORTRAN - 1957

But giant - But giant - As of 2004, the U. S. Bureau of Labor Statistics counts As of 2004, the U. S. Bureau of Labor Statistics counts 760,840 software engineers holding jobs in the U.S.; for comparison, in 760,840 software engineers holding jobs in the U.S.; for comparison, in the U.S. there are some 1.4 million practitioners employed in all other the U.S. there are some 1.4 million practitioners employed in all other engineering disciplines combined.engineering disciplines combined. - - http://en.wikipedia.org/wiki/Software_engineeringhttp://en.wikipedia.org/wiki/Software_engineering

Unanticipated growthUnanticipated growth

Still more art than scienceStill more art than science Everything we do is “new”. (We don’t build the exact same Everything we do is “new”. (We don’t build the exact same

house 30 times.)house 30 times.) Need to have more reproducible results Need to have more reproducible results Need to have more measurementsNeed to have more measurements

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Why do projects fail?Why do projects fail?Why do projects fail so often?Why do projects fail so often? Unrealistic or unarticulated project goalsUnrealistic or unarticulated project goals Inaccurate estimates of needed resourcesInaccurate estimates of needed resources Badly defined system requirementsBadly defined system requirements Poor reporting of the project's statusPoor reporting of the project's status Unmanaged risksUnmanaged risks Poor communication among customers, developers, and usersPoor communication among customers, developers, and users Use of immature technologyUse of immature technology Inability to handle the project's complexityInability to handle the project's complexity Sloppy development practicesSloppy development practices Poor project managementPoor project management Stakeholder politicsStakeholder politics Commercial pressuresCommercial pressuresList from: http://www.spectrum.ieee.org/sep05/1685List from: http://www.spectrum.ieee.org/sep05/1685

How many of these are caused by technical incompetence in your developers?A.0B.5C.8D.All of them

How many of these are caused by technical incompetence in your developers?A.0B.5C.8D.All of them

Question:Question:

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How do we fix it?How do we fix it?

Need to have more Need to have more reproducible resultsreproducible results Standard processes / procedures to produce good Standard processes / procedures to produce good

outcomesoutcomes Design patternsDesign patterns Object oriented programming (reuse)Object oriented programming (reuse)

More More measurementsmeasurements of both the software and the process of both the software and the process More More testingtesting at all stages of development at all stages of development By creating a better understanding of the By creating a better understanding of the processprocess we use we use

to create software, we’ll create better software faster.to create software, we’ll create better software faster.

“Software engineering is the application of a systematic, disciplined, quantifiable approach to the development, operation, and maintenance of software.” - IEEE Standard Glossary of Software Engineering Terminology

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Software Engineering: A Practitioner’s Software Engineering: A Practitioner’s Approach, 7/eApproach, 7/e

Chapter 1Chapter 1Software and Software Software and Software

EngineeringEngineering

copyright © 1996, 2001, 2005

R.S. Pressman & Associates, Inc.

For University Use OnlyMay be reproduced ONLY for student use at the university level

when used in conjunction with Software Engineering: A Practitioner's Approach.Any other reproduction or use is expressly prohibited.

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Why is software different thanWhy is software different thanhardware? Or manufacturing?hardware? Or manufacturing?

software is engineered software doesn’t wear out most software is still custom built software is complex

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Wear vs. Wear vs. DeteriorationDeterioration

idealized curve

change

actual curve

Failurerate

Time

increased failurerate due to side effects

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There are many types of There are many types of applicationsapplications system software - system software - OS, file management, networking, drivers, etc…OS, file management, networking, drivers, etc…

application software - application software - data processing, point of sale, other data processing, point of sale, other business functions…business functions…

engineering/scientific software - engineering/scientific software - CAD, stress analysis, CAD, stress analysis, orbital mechanicsorbital mechanics

embedded software - embedded software - microwave oven keypad, automobile control, microwave oven keypad, automobile control, cell phone software, etc…cell phone software, etc…

product-line software - product-line software - word processing, inventory control, etc…word processing, inventory control, etc…

WebApps (Web applications) - WebApps (Web applications) - many different things todaymany different things today

AI software - AI software - robotics, data mining, expert systemsrobotics, data mining, expert systems

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Legacy SoftwareLegacy Software

software must be software must be adaptedadapted to meet the needs of new to meet the needs of new computing environments or technology.computing environments or technology.

software must be software must be enhancedenhanced to implement new business to implement new business requirements.requirements.

software must be software must be extended to make it interoperableextended to make it interoperable with with other more modern systems or databases.other more modern systems or databases.

software must be software must be re-architectedre-architected to make it viable within a to make it viable within a network environmentnetwork environment.

Why must it change?

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Software – Software – A.True or A.True or B.False?B.False?

1.1. If we get behind schedule we can add more If we get behind schedule we can add more programmers to catch upprogrammers to catch up

2.2. A general statement of objectives is sufficient to begin A general statement of objectives is sufficient to begin writing programs - we can fill in the details laterwriting programs - we can fill in the details later

3.3. Project requirements change, but change can be easily Project requirements change, but change can be easily accommodated because software is flexibleaccommodated because software is flexible

4.4. Once we write the program and get it working our job Once we write the program and get it working our job is doneis done

5.5. Software engineering will make us create unnecessary Software engineering will make us create unnecessary documentation and will invariably slow us downdocumentation and will invariably slow us down

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Software MythsSoftware Myths

Affect managers, customers (and other non-Affect managers, customers (and other non-technical stakeholders) and practitionerstechnical stakeholders) and practitioners

Are believable because they often have elements Are believable because they often have elements of truth, of truth,

but …but … Invariably lead to bad decisions, Invariably lead to bad decisions,

therefore …therefore … Insist on reality as you navigate your way Insist on reality as you navigate your way

through software engineeringthrough software engineeringOne of the goals in this class is to learn you

how to determine what reality is!

Fixing the problemFixing the problem

Software engineering!Software engineering! Software engineering is really Software engineering is really

just a set of ideas and tools to just a set of ideas and tools to

use (when it makes sense) to use (when it makes sense) to

give you a higher likelihood of give you a higher likelihood of

success on a software project.success on a software project.

Will your project fail if you don’t use any software Will your project fail if you don’t use any software engineering techniques? No…. but you have a better engineering techniques? No…. but you have a better chance at success if you do.chance at success if you do.

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A Generic FrameworkA Generic Framework CommunicationCommunication

Heavy collaboration with the customer, other stakeholders and Heavy collaboration with the customer, other stakeholders and encompasses requirements gathering and related activitiesencompasses requirements gathering and related activities

PlanningPlanning Establish a plan for the work. Technical task to be conducted, risks, Establish a plan for the work. Technical task to be conducted, risks,

needed resources, work products to be created, and a scheduleneeded resources, work products to be created, and a schedule ModelingModeling

Creation of models to allow the customer and the developer to better Creation of models to allow the customer and the developer to better understand the requirements and design that will achieve those understand the requirements and design that will achieve those requirementsrequirements

ConstructionConstruction Combines code generation and testing required to uncover errors in the Combines code generation and testing required to uncover errors in the

codecode DeploymentDeployment

The software (as a complete entity or partially complete increment) is The software (as a complete entity or partially complete increment) is delivered to the customer who evaluates it and provides feedback.delivered to the customer who evaluates it and provides feedback.

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Framework ActivitiesFramework Activities

CommunicationCommunication PlanningPlanning ModelingModeling

Analysis of requirementsAnalysis of requirements DesignDesign

ConstructionConstruction Code generationCode generation TestingTesting

DeploymentDeployment

What are some artifacts (work tasks, work products, milestones & deliverables, QA checkpoints) of each activity? What tools may help support them?

What are some artifacts (work tasks, work products, milestones & deliverables, QA checkpoints) of each activity? What tools may help support them?

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Umbrella ActivitiesUmbrella Activities Software project management Formal technical reviews Software quality assurance Software configuration management Work product preparation and

production Reusability management Measurement Risk management

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The Process Model:The Process Model:AdaptabilityAdaptability

The framework activities will The framework activities will alwaysalways be be applied on applied on everyevery project ... BUT project ... BUT

The tasks (and degree of rigor) for each The tasks (and degree of rigor) for each activity will vary based on:activity will vary based on: the type of project the type of project characteristics of the projectcharacteristics of the project common sense judgment; common sense judgment;

concurrence of the project teamconcurrence of the project team

QuestionQuestion

Pick any one of the project types below and tell Pick any one of the project types below and tell me which process activity would be emphasized me which process activity would be emphasized or deemphasized and whyor deemphasized and why

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Project Types:Project Types:- 1.Space Shuttle control system1.Space Shuttle control system- 2.Web-based calendar2.Web-based calendar- 3.Embedded controller in your 3.Embedded controller in your refrigeratorrefrigerator- 4.Automatic “daily fortune” text-4.Automatic “daily fortune” text-messengermessenger

Framework ActivitiesFramework Activities CommunicationCommunication PlanningPlanning ModelingModeling

Analysis of requirementsAnalysis of requirements DesignDesign

ConstructionConstruction Code generationCode generation TestingTesting

DeploymentDeployment

How to solve any problemHow to solve any problem

Polya 1945 Polya 1945 Understand the problemUnderstand the problem Plan a solutionPlan a solution Carry out the planCarry out the plan Examine the result for accuracyExamine the result for accuracy

Do these agree with our basic framework? Do these agree with our basic framework? communication, planning, modeling, construction communication, planning, modeling, construction deployment? deployment?

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How do we improve our How do we improve our performance?performance?

We want to “provide guidance for developing or We want to “provide guidance for developing or improving processes that meet the business improving processes that meet the business goals of an organization”goals of an organization”

Capability Maturity Model IntegrationCapability Maturity Model Integration (CMMI) is a (CMMI) is a process improvement approach that approach that helps organizations improve their performancehelps organizations improve their performance

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The CMMIThe CMMI CMMI defines characteristics shown to achieve CMMI defines characteristics shown to achieve

good results.good results. The CMMI defines each process area in terms of The CMMI defines each process area in terms of

“specific goals” and the “specific practices” “specific goals” and the “specific practices” required to achieve these goals.required to achieve these goals.

Specific goalsSpecific goals establish the characteristics that establish the characteristics that must exist if the activities implied by a process must exist if the activities implied by a process area are to be effective. area are to be effective.

Specific practicesSpecific practices refine a goal into a set of refine a goal into a set of process-related activities.process-related activities.

PP - project planningREQM - Requirements MgmtMA - Measurement and AnalysisCM - Configuration MgmtPPQA - Process and Product QA

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The CMMIThe CMMI

The Waterfall ModelThe Waterfall Model

Do all process steps in the following order (this is Do all process steps in the following order (this is generally thought of as the most basic model)generally thought of as the most basic model)

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Communication Planning

ModelingConstruction

Deployment analysis design code

test

project initiation requirement gathering estimating

scheduling tracking

delivery support feedback

1998, the Standish Group analyzed 23,000 projects to determine failure 1998, the Standish Group analyzed 23,000 projects to determine failure factors. The top reasons for project failure, according to the report, factors. The top reasons for project failure, according to the report, were associated with waterfall practices. were associated with waterfall practices.

- http://www2.umassd.edu/SWPI/xp/articles/r6047.pdf- http://www2.umassd.edu/SWPI/xp/articles/r6047.pdf

Different families of modelsDifferent families of models

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Prescriptive Agile

Prescriptive Models 1970->Present

-Waterfall (1970)-Evolutionary (1975)-Incremental (1975)-Spiral (1988)-RAD (1991)

Agile Models 2001->Present

- eXtreme Programming (1999)- SCRUM (1990s)- DSDM (1997)- Crystal (2001)

All dates are approximate based on publications

Different families of modelsDifferent families of models

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Prescriptive Agile

Goal: Higher Quality Software

Philosophy:•Bring order to chaos•Provide repeatability/consistency•Provide ability to control•Provide ability to coordinate teams

Goal: Higher Quality Software

Philosophy:•Individuals and interaction over process and tools•Working software over large documentation•Customer collaboration over contract negotiation•Responding to change over following a plan

Which is probably better for large teams? A. Prescriptive B. Agile C. Same

Which is probably better for a web application?

Which is probably better for Mars rover control system?

Which is produces better software?

ProjectProject

Team decisions due tomorrow/today (depending Team decisions due tomorrow/today (depending on section)on section) Post to blackboard a document containing your team Post to blackboard a document containing your team

name, and the names and emails of the members of name, and the names and emails of the members of your teamyour team

4-5 students per team4-5 students per team Turn in your team interview sheets (handed out Sept Turn in your team interview sheets (handed out Sept

1/2) in class, if you are not part of a team. If I didn’t get 1/2) in class, if you are not part of a team. If I didn’t get an email from your team, I will use these sheets for the an email from your team, I will use these sheets for the rest of you to assign teams for you.rest of you to assign teams for you.

I will then set up accounts for teams on XP-dev; you will I will then set up accounts for teams on XP-dev; you will be emailed informationbe emailed information

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HomeworkHomework

Pressman ch 1 exercises: 5, 8, 10Pressman ch 1 exercises: 5, 8, 10 Due next Thursday by 10pmDue next Thursday by 10pm Submit on blackboardSubmit on blackboard

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